Method and apparatus for communication in next generation mobile communication system

ABSTRACT

The present disclosure relates to a communication method and system for converging a 5 th -Generation (5G) communication system for supporting higher data rates beyond a 4 th -Generation (4G) system with a technology for Internet of Things (IoT). The present disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. 
     A method for operating a terminal is provided. The method includes receiving a first radio resource control (RRC) message including information for RRC connection suspension, maintaining a signaling radio bearer (SRB) 0 and suspending a data radio bearer (DRB) and at least one other SRB based on the first RRC message, transmitting, to a base station, a second RRC message for requesting RRC connection resumption through the SRB0, receiving, from the base station, a third RRC message for the RRC connection resumption through an SRB1, and resuming an SRB2 and the DRB based on the third RRC message.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit under 35 U.S.C. § 119(a) of a Korean patent application filed on Sep. 26, 2016 in the Korean Intellectual Property Office and assigned Serial number 10-2016-0123440, the entire disclosure of which is hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a method and an apparatus for communication in a next-generation mobile communication system. More particularly, the present disclosure relates to a method and an apparatus for configuring and transmitting a physical uplink control channel (PUCCH) in a next-generation mobile communication system using an analog beamforming technology together with the use of a plurality of antennas.

BACKGROUND

To meet the demand for wireless data traffic having increased since deployment of fourth-generation (4G) communication systems, efforts have been made to develop an improved fifth generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post long term evolution (LTE) System’. The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems. In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud radio access networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, coordinated multi-points (CoMP), reception-end interference cancellation and the like. In the 5G system, hybrid frequency shift keying (FSK) and quadrature amplitude modulation (QAM) modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.

The Internet, which is a human centered connectivity network where humans generate and consume information, is now evolving to the internet of things (IoT) where distributed entities, such as things, exchange and process information without human intervention. The internet of everything (IoE), which is a combination of the IoT technology and the Big Data processing technology through connection with a cloud server, has emerged. As technology elements, such as “sensing technology”, “wired/wireless communication and network infrastructure”, “service interface technology”, and “Security technology” have been demanded for IoT implementation, a sensor network, a machine-to-machine (M2M) communication, machine type communication (MTC), and so forth have been recently researched. Such an IoT environment may provide intelligent Internet technology services that create a new value to human life by collecting and analyzing data generated among connected things. IoT may be applied to a variety of fields including smart home, smart building, smart city, smart car or connected cars, smart grid, health care, smart appliances and advanced medical services through convergence and combination between existing information technology (IT) and various industrial applications.

In line with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as a sensor network, MTC, and M2M communication may be implemented by beamforming, MIMO, and array antennas. Application of a RAN as the above-described Big Data processing technology may also be considered to be as an example of convergence between the 5G technology and the IoT technology.

The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.

SUMMARY

Aspects of the present disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below.

At present, in a long term evolution (LTE) system, a physical uplink control channel (PUCCH) resource is allocated and configured using a time resource and a frequency resource, and a PUCCH is transmitted using the PUCCH resource. However, in the case of using an analog beamforming technology together with a plurality of antennas in the next-generation mobile communication system, it is necessary to consider a beam direction. Further, if a new cell is defined or a new base station structure is defined, a method for configuring and transmitting a PUCCH becomes necessary to be suitable thereto. Accordingly, an aspect of the present disclosure is to provide a method and an apparatus for configuring and transmitting a PUCCH in the next-generation mobile communication system.

Another aspect of the present disclosure is to provide an apparatus and a method for packet loss recovery during providing of multiple connections in a wireless communication system.

Another aspect of the present disclosure proposes a method for a terminal to measure a signal in a wireless communication system performing a beam-based communication.

Another aspect of the present disclosure is to provide a signaling radio bearer (SRB)-related configuration and operation in order for a terminal and a base station to correctly send and receive a control message in the case where the base station and the terminal perform, if needed, a procedure of resuming their connection after suspending the connection in a wireless communication system.

Another aspect of the present disclosure is to provide operations of a base station and a terminal in order for the base station and the terminal to correctly send and receive a control message in the case where they resume, if needed, their connection after suspending the connection in a wireless communication system.

In accordance with an aspect of the present disclosure, a method for operating a terminal is provided. The method includes receiving a first radio resource control (RRC) message including information for RRC connection suspension, maintaining a signaling radio bearer (SRB) 0 and suspending a data radio bearer (DRB) and at least one other SRB based on the first RRC message, transmitting, to a base station, a second RRC message for requesting RRC connection resumption through the SRB0, receiving, from the base station, a third RRC message for the RRC connection resumption through an SRB1, and resuming an SRB2 and the DRB based on the third RRC message.

In accordance with another aspect of the present disclosure, a terminal is provided. The terminal includes a transceiver configured to transmit and receive a signal, and a controller configured to receive a first radio resource control (RRC) message including information for RRC connection suspension, maintain a signaling radio bearer (SRB) 0 and to suspend a data radio bearer (DRB) and at least one other SRB based on the first RRC message, transmit, to a base station, a second RRC message for requesting RRC connection resumption through the SRB0, receive, from the base station, a third RRC message for the RRC connection resumption through an SRB1, and resume an SRB2 and the DRB based on the third RRC message.

In accordance with another embodiment of the present disclosure, a method for operating a base station is provided. The method includes transmitting, to a terminal, a first radio resource control (RRC) message including information for RRC connection suspension, receiving, from the terminal, a second RRC message for requesting RRC connection resumption through a signaling radio bearer (SRB) 0, transmitting, to the terminal, a third RRC message for the RRC connection resumption through an SRB1, and resuming an SRB2 and a data radio bearer (DRB) based on the third RRC message. The DRB and at least one other SRB are suspended while the SRB0 is maintained based on the first RRC message, and the SRB1 is not in a suspended state before the third RRC message is received.

In accordance with another embodiment of the present disclosure, a base station is provided. The base station includes a transceiver configured to transmit and receive a signal, and a controller configured to transmit, to a terminal, a first radio resource control (RRC) message including information for RRC connection suspension, receive, from the terminal, a second RRC message for requesting RRC connection resumption through a signaling radio bearer (SRB) 0, transmit, to the terminal, a third RRC message for the RRC connection resumption through an SRB1, and resume an SRB2 and a data radio bearer (DRB) based on the third RRC message. The DRB and at least one other SRB are suspended while the SRB0 is maintained based on the first RRC message, and the SRB1 is not in a suspended state before the third RRC message is received.

In accordance with an aspect of the present disclosure, an efficient PUCCH transmission becomes possible through the method for configuring and transmitting the PUCCH suitable to the next-generation mobile communication system (NR).

In accordance with another aspect of the present disclosure, the terminal can prevent a data loss even in the case where the connection configuration is changed or cancelled during providing of multiple connections.

In accordance with another aspect of the present disclosure, the terminal can measure the strength and quality of a reference signal (RS) in accordance with a specific downlink reception beam configuration in a predetermined period without continuously measuring all beams after determining suitable transmission beam and reception beam, and thus power consumption of the terminal can be reduced.

In accordance with another aspect of the present disclosure, the SRB-related configuration and operation are specified in the case where the base station and the terminal resume, if needed, their connection after suspending the connection in the wireless communication system, and thus the terminal and the base station can correctly send and receive the control message.

In accordance with another aspect of the present disclosure, the operations of the base station and the terminal are clearly examined in the case where they resume their connection after suspending the connection in the wireless communication system, and thus the base station and the terminal can correctly send and receive the control message.

Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certain embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1A is a diagram illustrating the structure of a next-generation mobile communication system to which the present disclosure can be applied according to an embodiment of the present disclosure;

FIG. 1B is a diagram explaining beam sweeping of a next-generation mobile communication system to which the present disclosure can be applied according to an embodiment of the present disclosure;

FIG. 1C is a diagram explaining a subframe structure of a next-generation mobile communication system to which the present disclosure can be applied according to an embodiment of the present disclosure;

FIG. 1D is a diagram illustrating a structure of another next-generation mobile communication system to which the present disclosure can be applied according to an embodiment of the present disclosure;

FIG. 1E is a diagram explaining a method for configuring and transmitting a physical uplink control channel (PUCCH) in a radio resource control (RRC) layer of a central unit (CU) according to a (1-1)-th embodiment of the present disclosure;

FIG. 1F is a diagram explaining a method 1 for an RRC layer of a CU and a media access control (MAC) layer of a distributed unit (DU) to configure and transmit a PUCCH according to a (1-2)-th embodiment of the present disclosure;

FIG. 1G is a diagram explaining a method 2 for an RRC layer of a CU and a MAC layer of a DU to configure and transmit a PUCCH according to a (1-3)-th embodiment of the present disclosure;

FIG. 1H is a diagram explaining a method 3 for an RRC layer of a CU and a MAC layer of a DU to configure and transmit a PUCCH according to a (1-4)-th embodiment of the present disclosure;

FIG. 1I is a diagram explaining an operation of a terminal according to the above-described embodiments of the present disclosure;

FIG. 1J is a block diagram illustrating a configuration of a terminal according to an embodiment of the present disclosure;

FIG. 1K is a block diagram illustrating a configuration of a base station transceiver according to an embodiment of the present disclosure;

FIG. 2A is a diagram illustrating a structure of a long term evolution (LTE) system for reference according to an embodiment of the present disclosure;

FIG. 2B is a diagram illustrating a radio protocol structure of an LTE system for reference according to an embodiment of the present disclosure;

FIG. 2C is a diagram of a frame structure used in a fifth-generation (5G) system to which the present disclosure is applied according to an embodiment of the present disclosure;

FIG. 2D is a diagram explaining a message flow between a terminal and a base station in the case of using a method for selectively determining a beam to be measured in accordance with measurement configuration according to an embodiment of the present disclosure;

FIG. 2E is a diagram explaining an order of operations of a terminal to which the present disclosure is applied according to an embodiment of the present disclosure;

FIG. 2F is a diagram illustrating a configuration of a terminal according to an embodiment of the present disclosure;

FIG. 3A is a diagram explaining a multi-connectivity operation scenario in a next-generation mobile communication system according to an embodiment of the present disclosure;

FIG. 3B is a diagram explaining a terminal having a plurality of radio frequency (RF) chains to support multi-connectivity according to an embodiment of the present disclosure;

FIG. 3C is a diagram explaining application of a time domain multiplexing (TDM) method to support multi-connectivity according to an embodiment of the present disclosure;

FIG. 3D is a diagram explaining a terminal having a single RF chain to apply a TDM method according to an embodiment of the present disclosure;

FIG. 3E is a diagram explaining a terminal having a single TX chain and plural RX chains to apply a TDM method according to an embodiment of the present disclosure;

FIG. 3F is a diagram explaining a (3-1)-th embodiment to configure TDM type multi-connectivity according to an embodiment of the present disclosure;

FIG. 3G is a diagram explaining an operation of a terminal according to the (3-1)-th embodiment of the present disclosure;

FIG. 3H is a diagram explaining an operation of a first base station according to the (3-1)-th embodiment of the present disclosure;

FIG. 3I is a diagram explaining a (3-2)-th embodiment to configure TDM type multi-connectivity according to an embodiment of the present disclosure;

FIG. 3J is a diagram explaining an operation of a first base station according to the (3-2)-th embodiment of the present disclosure;

FIG. 3K is a diagram explaining a scenario of releasing a TDM method according to an embodiment of the present disclosure;

FIG. 3L is a diagram illustrating a configuration of a terminal according to an embodiment of the present disclosure;

FIG. 3M is a diagram illustrating a configuration of a base station according to an embodiment of the present disclosure;

FIG. 4A is a diagram illustrating a structure of a next-generation mobile communication system according to an embodiment of the present disclosure;

FIG. 4B is a diagram of a frame structure used by an NR system to which the present disclosure is applied according to an embodiment of the present disclosure;

FIG. 4C is a diagram explaining a radio link monitoring (RLM) operation in an existing LTE system according to an embodiment of the present disclosure;

FIG. 4D is a diagram explaining a radio link failure (RLF) operation in an existing LTE system according to an embodiment of the present disclosure;

FIG. 4E is a diagram conceptually explaining an RLF operation in a next-generation mobile communication system according to an embodiment of the present disclosure;

FIG. 4F is a diagram explaining a serving beam and a beam group in RLM/RLF in a next-generation mobile communication system according to an embodiment of the present disclosure;

FIG. 4G is a diagram explaining an RLM operation according to an embodiment of the present disclosure;

FIG. 4H is a diagram explaining an operation of a terminal in RLM/RLF according to an embodiment of the present disclosure;

FIG. 4I is a diagram explaining a first process according to an embodiment of the present disclosure;

FIG. 4J is a diagram explaining a first process according to an embodiment of the present disclosure;

FIG. 4K is a diagram illustrating a configuration of a terminal according to an embodiment of the present disclosure;

FIG. 4L is a diagram illustrating a configuration of a base station according to an embodiment of the present disclosure;

FIG. 5A is a diagram illustrating a structure of an LTE system according to an embodiment of the present disclosure;

FIG. 5B is a diagram illustrating a radio protocol structure of an LTE system according to an embodiment of the present disclosure;

FIG. 5C is a diagram explaining operations of an RLF-related terminal and network according to an embodiment of the present disclosure;

FIG. 5D is a diagram explaining operations of a terminal and a network related to an RRC connection suspending/resuming procedure according to an embodiment of the present disclosure;

FIG. 5E is a diagram explaining an operation of a terminal according to an embodiment of the present disclosure;

FIG. 5F is a diagram illustrating a configuration of a terminal according to an embodiment of the present disclosure;

FIG. 5G is a diagram illustrating a configuration of a base station according to an embodiment of the present disclosure;

FIG. 6A is a diagram illustrating a structure of an LTE system according to an embodiment of the present disclosure;

FIG. 6B is a diagram illustrating a radio protocol structure of an LTE system according to an embodiment of the present disclosure;

FIG. 6C is a diagram illustrating a procedure in which a network suspends connection with a terminal according to a (6-1)-th embodiment of the present disclosure;

FIG. 6D is a diagram illustrating a procedure in which a terminal and a network resume connection according to the (6-1)-th embodiment of the present disclosure;

FIG. 6E is a diagram explaining an operation of a terminal according to the (6-1)-th embodiment of the present disclosure;

FIG. 6F is a diagram illustrating a procedure in which a network suspends connection with a terminal according to a (6-2)-th embodiment of the present disclosure;

FIG. 6G is a diagram illustrating a procedure in which a terminal and a network resume connection according to the (6-2)-th embodiment of the present disclosure;

FIG. 6H is a diagram explaining an operation of a terminal according to the (6-2)-th embodiment of the present disclosure;

FIG. 6I is a diagram illustrating a configuration of a terminal according to an embodiment of the present disclosure; and

FIG. 6J is a diagram illustrating a configuration of a base station in a wireless communication system according to an embodiment of the present disclosure.

Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces.

The aspects and features of the present disclosure and methods for achieving the aspects and features will be apparent by referring to the embodiments to be described in detail with reference to the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed hereinafter, but can be implemented in diverse forms. The matters defined in the description, such as the detailed construction and elements, are nothing but specific details provided to assist those of ordinary skill in the art in a comprehensive understanding of the disclosure, and the present disclosure is only defined within the scope of the appended claims. In the entire description of the present disclosure, the same drawing reference numerals are used for the same elements across various figures.

First Embodiment

An embodiment of present disclosure relates to a method and an apparatus for configuring and transmitting a physical uplink control channel (PUCCH) in a next-generation mobile communication system (new radio (NR) or fifth-generation (5G)), and a terminal may include the following operations.

-   -   An operation at which the terminal receives first information         through an radio resource control (RRC) message (layer 3         message).     -   The first information may include a format of a type 1 PUCCH and         a format of a type 2 PUCCH. Information on the format may be an         integer between a predetermined minimum value and a         predetermined maximum value.     -   The information on the format may indicate the size of the PUCCH         and the contents to be put in the PUCCH.     -   The first information may indicate a frequency resource for         measurement of channel state information (CSI).     -   The type 1 PUCCH may be periodically transmitted. Further, the         type 1 PUCCH may be periodically transmitted in accordance with         a specific period indicated by second information.     -   Transmission of the type 1 PUCCH may be triggered by MAC control         information (or MAC control element) including the second         information.     -   The type 1 PUCCH may include a periodic CSI. Information, such         as channel quality indicator (CQI), precoding matrix indicator         (PMI), and rank indicator (RI), may be included in the CSI.     -   The type 2 PUCCH may be aperiodically transmitted. Further, it         may be transmitted n times. The integer n may be indicated in         the first information or the second information.     -   Transmission of the type 2 PUCCH may be triggered by downlink         control information (DCI) including third information.     -   The type 2 PUCCH may include aperiodic CSI.     -   An operation at which the terminal receives the second         information through a media access control (MAC) control message         (MAC control information or MAC control element).     -   The second information may include a transmission period of the         type 1 PUCCH or transmission resource information (frequency         resource or time resource) for the type 1 PUCCH.     -   An operation at which the terminal receives the third         information through a PHY control message (physical control         information or DCI in PDCCH).     -   The third information may include the number of transmissions of         the type 2 PUCCH or transmission resource information (frequency         resource or time resource) for the type 2 PUCCH.     -   An operation at which the terminal transmits the type 1 PUCCH or         type 2 PUCCH.     -   The terminal may apply the first information or the second         information, and may transmit the type 1 PUCCH using an uplink         beam with a specific direction.     -   The terminal may apply the first information or the third         information, and may transmit the type 2 PUCCH using an uplink         beam with a specific direction.     -   The uplink beam with the specific direction may be a beam         determined by a random access procedure most recently performed         by the terminal. Further, the uplink beam with the specific         direction may be a beam having an uplink direction that         coincides with a downlink beam direction of a serving beam by         which the terminal is currently being serviced. Further, the         uplink beam with the specific direction may be an uplink beam         selected through a best beam pair selection process performed by         the terminal and the base station. The best beam selection         process means a process in which the base station transmits         downlink beams supported by the base station in a specific time         period, and the terminal checks all possible pairs of the         downlink beams and the uplink beams using the uplink beams         supported by the terminal, and then selects a pair having the         highest signal quality.     -   An operation at which the terminal receives a first message from         a network.     -   The first message may be an RRC message.     -   The first message includes at least the first information.     -   An operation at which the terminal confirms whether the second         information is included in the first message.     -   An operation at which the terminal transmits the type 1 PUCCH         after receiving the first message if the second information is         included in the first message.     -   Transmission of the type 1 PUCCH is performed based on the first         information of the first message and the second information of         the first message.     -   Transmission of the type 1 PUCCH is performed by the uplink beam         with the specific direction.     -   The uplink beam with the specific direction may be a beam         determined by the random access procedure most recently         performed by the terminal. Further, the uplink beam with the         specific direction may be a beam having an uplink direction that         coincides with a downlink beam direction of a serving beam by         which the terminal is currently being serviced. Further, the         uplink beam with the specific direction may be indicated by a         network. Further, the uplink beam with the specific direction         may be an uplink beam selected through a best beam pair         selection process performed by the terminal and the base         station. The best beam selection process means a process in         which the base station transmits downlink beams supported by the         base station in a specific time period, and the terminal checks         all possible pairs of the downlink beams and the uplink beams         using the uplink beams supported by the terminal, and then         selects a pair having the highest signal quality.     -   An operation at which the terminal transmits the type 1 PUCCH         after receiving the second information if the second information         is included in the first message.     -   Transmission of the type 1 PUCCH is performed based on the first         information of the first message and the second information of         the second message.     -   The second message may be a MAC control message.     -   Transmission of the type 1 PUCCH is performed by the uplink beam         with the specific direction.     -   The uplink beam with the specific direction may be a beam         determined by the random access procedure most recently         performed by the terminal. Further, the uplink beam with the         specific direction may be a beam having an uplink direction that         coincides with a downlink beam direction of a serving beam by         which the terminal is currently being serviced. Further, the         uplink beam with the specific direction may be indicated by the         network. Further, the uplink beam with the specific direction         may be an uplink beam selected through a best beam pair         selection process performed by the terminal and the base         station. The best beam selection process means a process in         which the base station transmits downlink beams supported by the         base station in a specific time period, and the terminal checks         all possible pairs of the downlink beams and the uplink beams         using the uplink beams supported by the terminal, and then         selects a pair having the highest signal quality.

An embodiment of the present disclosure has a procedure of configuring and transmitting the PUCCH as described above, and more detailed contents thereof will be described hereinafter with reference to the drawings.

FIG. 1A is a diagram illustrating the structure of a next-generation mobile communication system to which the present disclosure can be applied according to an embodiment of the present disclosure.

Referring to FIG. 1A, a radio access network of a next-generation mobile communication system is composed of a new radio node B (NR NB) 1 a-10 and a new radio core network (NR CN) 1 a-05. A user terminal (new radio user equipment (NR UE)) 1 a-15 connects to an external network through the NR NB 1 a-10 and the NR CN 1 a-05.

In FIG. 1A, the NR NB 1 a-10 corresponds to an evolved node B (eNB) of the existing LTE system. The NR NB may be connected to the NR UE 1 a-15 through a radio channel, and thus can provide a more superior service than the service of the existing node B. Since all user traffics are serviced through shared channels, a device that performs scheduling through consolidation of status information, such as a buffer state, an available transmission power state, and a channel state, of each UE is necessary, and the NR NB 1 a-10 takes charge of this. One NR NB generally controls plural cells. In order to implement ultrahigh-speed data transmission as compared with the existing LTE, the NR NB may have a bandwidth that is equal to or higher than the existing maximum bandwidth, and a beamforming technology may be additionally grafted in consideration of orthogonal frequency division multiplexing (OFDM) as a radio connection technology. Further, an adaptive modulation & coding (AMC) method that determines a modulation scheme and a channel coding rate to match the channel state of the terminal is applied to the NR NB. The NR CN 1 a-05 performs mobility support, bearer configuration, and quality of service (QoS) configuration. The NR CN is a device that takes charge of not only terminal mobility management but also various kinds of control functions, and is connected to a plurality of base stations. Further, the next-generation mobile communication system may interlock with the existing LTE system, and the NR CN is connected to a mobility management entity (MME) 1 a-25 through a network interface. The MME is connected to an eNB 1 a-30 that is the existing base station.

FIG. 1B is a diagram explaining beam sweeping of a next-generation mobile communication system to which the present disclosure can be applied according to an embodiment of the present disclosure.

Referring to FIG. 1B, the NR takes aim at supporting a data transmission speed that is increased as compared with that of the existing LTE. As a method for heightening the data transmission speed in the NR, a method for transmitting a signal using a wide frequency band existing in a frequency band of 6 GHz or more has been considered. That is, it has been considered to increase the transmission rate using a millimeter wave (hereinafter referred to as “mmWave”) band, such as a 28 GHz band or 60 GHz band. The frequency band that is considered for the mmWave has a relatively large signal attenuation size per distance, and thus in order to secure a coverage, a transmission based on a directional beam generated using multiple antennas is necessary. The transmission based on the directional beam has a problem that it is difficult to transmit or receive a signal in a location where a beam is not formed, and in order to overcome this, a beam sweeping technique is used. The beam sweeping is a technique in which a transmission device transmits a directional beam having a constant beam width while successively sweeping or rotating the directional beam to cause a reception device that is within a beam arrival distance of the transmission device to receive the beam. For example, a transmission reception point (TRP) 1 b-05 is a device that transmits and receives a radio signal in a network, and may be a 5G NB or a device connected to the 5G NB. The TRP may transmit a directional beam having a specific width in a specific direction at a certain time t1, and transmit the directional beam having the same width in another direction at time t2, so that the beam covers all directions for a specific time period. As a result, a downlink signal transmitted by the base station arrives at a terminal 1 b-15 at time t9, and arrives at a terminal 1 b-10 at time t4.

The beam sweeping is mainly used in the case where the base station does not know the direction of the directional beam to be applied to the terminal, and a common overhead signal (OSF) to be transmitted to a terminal in an idle state (idle state terminal) is transmitted through the beam sweeping.

In order to heighten the beam efficiency, not only a transmission directional beam but also a reception directional beam may be used. If the reception directional beam is used, the directivity/direction of the transmission beam and the directivity/direction of the reception beam should be synchronized with each other. For example, if the directivity of the reception beam is not synchronized with the directivity of the transmission beam although the terminal (1 b-20) is located in a region of the transmission beam, the terminal is unable to receive the transmission beam. In contrast, if the directivity of the transmission beam is synchronized with the directivity of the reception beam and the terminal (1 b-25) is located in a region of the transmission beam, data can be transmitted and received with much higher efficiency as compared with a case where the reception beam is not used.

In order to find a reception beam that is synchronized with the transmission beam, the reception device searches for a reception beam that provides the most prominent reception quality through applying different reception beams with respect to the same transmission beam. This process is called a reception beam sweeping.

FIG. 1C is a diagram explaining a subframe structure of a next-generation mobile communication system to which the present disclosure can be applied according to an embodiment of the present disclosure.

Referring to FIG. 1C, in a mobile communication system in which a directional beam, an analog beam, or a hybrid beam is used, the common overhead signal (OSF) is transmitted through beam sweeping at a specific subframe, and user data may be transmitted to or received from a specific terminal using the directional beam of a single direction in another subframe.

The subframe that has received the OSF 1 c-05 is repeatedly transmitted in a predetermined period 1 c-10. One subframe is composed of a plurality of symbols, and in the OSF, one directional beam is transmitted for one symbol. For example, a directional beam (or analog beam) is transmitted, in which first to eleventh symbols 1 c-15 to 1 c-25 respectively correspond to times t1 to t11, the respectively symbols have the same beam width, but cover different regions, and the directivities are configured in different directions.

Overhead signals below may be transmitted for the respective symbols of the OSF.

-   -   A signal for downlink synchronization establishment, such as a         primary synchronization signal (PSS) and a secondary         synchronization signal (SSS).     -   A beam reference signal (BRS) capable of measuring a reception         signal strength or reception signal quality for each beam.     -   System information, master information block (MIB), or physical         broadcast channel (PBCH).     -   In the PBCH, essential information for the terminal to access to         a 1 d system, for example, downlink beam bandwidth or system         frame number, is included.

For reference, a public land mobile network (PLMN) identifier may be broadcast through another channel other than the MIB.

In a subframe that is not the OSF being periodically transmitted, the same beam is transmitted over several successive symbols, and user data for a specific terminal in a connected state may be transmitted through the beam. Hereinafter, the subframe is called a data subframe (DSF) 1 c-30.

FIG. 1D is a diagram illustrating the structure of another next-generation mobile communication system to which the present disclosure can be applied according to an embodiment of the present disclosure.

Referring to FIG. 1D, a cell that is serviced by an NR base station (NR gNB) 1 d-05 operating based on a beam may be composed of several TRPs 1 d-10, 1 d-15, 1 d-20, 1 d-25, 1 d-30, 1 d-35, and 1 d-40. The TRPs 1 d-10, 1 d-15, 1 d-20, 1 d-25, 1 d-30, 1 d-35, and 1 d-40 indicate blocks obtained by separating partial functions of transmitting and receiving physical signals from the existing LTE base station eNB, and are composed of a plurality of antennas. The NR base station may be expressed as a central unit (CU), and the TRP may be expressed as a distributed unit (DU). The functions of the NR gNB and the TRP may be configured by separating respective layers 1 d-45 from packet data convergence protocol (PDCP)/radio link control (RLC)/MAC/physical (PHY) layers. That is, the TRPs 1 d-15 and 1 d-25 can perform the function of the corresponding layer only with the PHY layer, the TRPs 1 d-10, 1 d-35, and 1 d-40 can perform the functions of the corresponding layers only with the PHY layer and the MAC layer, and the TRPs 1 d-20 and 1 d-30 can perform the functions of the corresponding layers only with the PHY layer, MAC layer, and RLC layer. In particular, the TRPs 1 d-10, 1 d-15, 1 d-20, 1 d-25, 1 d-30, 1 d-35, and 1 d-40 may use a beamforming technology that transmits and receives data through generation of narrow beams in several directions using a plurality of transmission/reception antennas. A user terminal 1 d-50 connects to the NR gNB 1 d-05 and an external network through the TRPs 1 d-10, 1 d-15, 1 d-20, 1 d-25, 1 d-30, 1 d-35, and 1 d-40. In order to provide services to users, the NR gNB 1 d-05 support a connection between the terminals and the core network (CN) by performing scheduling through consolidation of status information, such as a buffer state, an available transmission power state, and a channel state, of each terminal.

An embodiment of the present disclosure proposes the above-described next-generation mobile communication system structure, and proposes a method and an apparatus for configuring and transmitting a PUCCH in the above-described system. A transmission resource for transmitting the PUCCH may be configured based on a time resource and a frequency resource. However, in the next-generation mobile communication system, beamforming technology using narrow beams as shown in FIG. 1B can be applied, and thus it is necessary to consider the time resource, the frequency resource, and even the beam direction when transmitting the PUCCH. Further, in the next-generation mobile communication system, one CU (or gNB) may be connected to several DUs (TRPs) as shown in FIG. 1D, and layers and functions of the respective TRPs may differ from each other. Accordingly, when the PUCCH is configured, the followings should be considered.

-   -   A PUCCH may be received and processed in a TRP.     -   A PUCCH transmission resource may be controlled by a TRP.     -   A PUCCH transmission beam may be controlled by a TRP.

In this structure, it is difficult for one CU to manage all terminals existing in a large region as shown in FIG. 1D through control signals. That is, due to backhaul delay between the CU and the DU (TRP), it is difficult for the CU to send a control signal to the terminal, and since the CU should perform lots of signaling processes with respect to the terminals, complexity may be greatly increased.

FIG. 1E is a diagram illustrating a method for configuring a PUCCH in an RRC layer of a CU, and transmitting configuration information according to the (1-1)-th embodiment of the present disclosure.

Referring to FIG. 1E, a CU 1 e-03 or gNB may have PDCP/RLC/MAC layers, and the DUs or TRP 1 e-02 may have only a PHY layer. Accordingly, the CU can manage scheduling of transmission resources. In the next-generation mobile communication system, if it is necessary to configure a PUCCH of a terminal 1 e-01 for a specific reason, the CU 1 e-03 determines PUCCH transmission configuration information of the corresponding terminal. The PUCCH transmission configuration information may include a PUCCH transmission period, PUCCH formats (format for periodic CSI, and format for aperiodic CSI), a transmission resource size, transmission resource information (time information and frequency information), transmission beam information, reception beam information, and the number of transmissions of the aperiodic CSI. The transmission resource information may include the number of subframes for indicating the period, a system frame number indicating an activation time, subframe number (SFN), resource block (RB) index indicating a frequency resource, and a symbol index indicating a time resource.

If the PUCCH transmission configuration information is determined, the CU 1 e-03 transfers the information to the TRP 1 e-02, at operation 1 e-05. Further, the CU 1 e-03 configures the PUCCH through transmission of the information to the terminal 1 e-01 as an RRC message, at operation 1 e-10. The terminal 1 e-01, for which the PUCCH is configured from the RRC message, may report the periodic CSI to the TRP 1 e-02 as a PUCCH format and a transmission resource for the periodic CSI using the PUCCH transmission configuration information received from operation 1 e-10, at operation 1 e-15. When reporting the periodic CSI, the terminal 1 e-01 may transmit it using an uplink beam with a specific direction.

The uplink beam with the specific direction may be a beam determined by a random access procedure most recently performed by the terminal 1 e-01. Further, the uplink beam with the specific direction may be a beam having an uplink direction that coincides with a downlink beam direction of a serving beam by which the terminal 1 e-01 is currently being serviced. Further, the uplink beam with the specific direction may be indicated by the network. Further, the uplink beam with the specific direction may be an uplink beam selected through a best beam pair selection process performed by the terminal 1 e-01 and the base station. The best beam selection process means a process in which the base station transmits downlink beams supported by the base station in a specific time period, and the terminal 1 e-01 checks all possible pairs of the downlink beams and the uplink beams using the uplink beams supported by the terminal, and then selects a pair having the highest signal quality.

If it is necessary for the CU 1 e-03 to receive the aperiodic CSI from the terminal 1 e-01 for a specific reason, the CU 1 e-03 configures the aperiodic CSI to the TRP 1 e-02, and the TRP allocates a PUCCH or PUSCH transmission resource for the aperiodic CSI to the terminal 1 e-01 from a PDCCH to DCI, at operations 1 e-20 and 1 e-25. The terminal 1 e-01 reports the aperiodic CSI to the TRP 1 e-02 using the PUCCH format for the aperiodic CSI configured in operation 1 e-10 and the transmission resource configured in operation 1 e-20, at operation 1 e-30. The aperiodic CSI may be transmitted n times successively or according to a determined rule. The integer n may be included in PUCCH transmission configuration related information. The integer n may be indicated in the first information or the second information.

When reporting the aperiodic CSI, the terminal 1 e-01 may transmit it using the uplink beam with the specific direction. The uplink beam with the specific direction may be a beam determined by a random access procedure most recently performed by the terminal 1 e-01. Further, the uplink beam with the specific direction may be a beam having an uplink direction that coincides with a downlink beam direction of a serving beam by which the terminal 1 e-01 is currently being serviced. Further, the uplink beam with the specific direction may be indicated by the network. Further, the uplink beam with the specific direction may be an uplink beam selected through a best beam pair selection process for selecting the optimum beam pair that is performed by the terminal 1 e-01 and the base station. The best beam selection process means a process in which the base station transmits downlink beams supported by the base station in a specific time period, and the terminal 1 e-01 checks all possible pairs of the downlink beams and the uplink beams using the uplink beams supported by the terminal 1 e-01, and then selects a pair having the highest signal quality.

FIG. 1F is a diagram illustrating a method 1 for an RRC layer of a CU and a MAC layer of a DU to configure a PUCCH, and to transmit configuration information according to a (1-2)-th embodiment of the present disclosure.

Referring to FIG. 1F, the DUs or TRPs 1 d-10, 1 d-20, 1 d-30, 1 d-35, and 1 d-40 may have MAC layers. Accordingly, a TRP 1 f-02 can manage scheduling of transmission resources. In the next-generation mobile communication system, if it is necessary to configure a PUCCH of a terminal 1 f-01 for a specific reason, a CU 1 f-03 determines PUCCH transmission configuration information of the terminal 1 f-01. The PUCCH transmission configuration information determined by the CU 1 f-03 may include a PUCCH transmission period (the number of subframes for indicating a period, a system frame number indicating an activation time, and SFN), PUCCH formats (format for periodic CSI and format for aperiodic CSI), a transmission resource size, transmission beam information, reception beam information, and the number of transmissions of the aperiodic CSI. If the PUCCH transmission configuration information is determined, the CU 1 f-03 transfers the information to the TRP 1 f-02, at operation 1 f-05.

The TRP 1 f-02 receives the PUCCH transmission configuration information and determines actual transmission resource information of the PUCCH. The transmission resource information may include a system frame number indicating an activation time, SFN, RB index indicating a frequency resource, a symbol index indicating a time resource, transmission beam information, and reception beam information. If the transmission resource information is determined, the TRP 1 f-02 configures the PUCCH of the terminal 1 f-01 through transmission of the PUCCH transmission resource information together with the PUCCH transmission configuration information received from operation 1 f-05 to the terminal 1 f-01 as a MAC control message (MAC control information or MAC control element), at operation 1 f-10.

The terminal 1 f-01, for which the PUCCH is configured from the MAC control message, may report the periodic CSI to the TRP 1 f-02 as a PUCCH format and a transmission resource for the periodic CSI using the PUCCH transmission configuration information received from the operation 1 f-10, at operation 1 f-15. When reporting the periodic CSI, the terminal 1 f-01 may transmit it using an uplink beam with a specific direction. The uplink beam with the specific direction may be a beam determined by a random access procedure most recently performed by the terminal 1 f-01. Further, the uplink beam with the specific direction may be a beam having an uplink direction that coincides with a downlink beam direction of a serving beam by which the terminal 1 f-01 is currently being serviced. Further, the uplink beam with the specific direction may be indicated by the network. Further, the uplink beam with the specific direction may be an uplink beam selected through a best beam pair selection process performed by the terminal 1 f-01 and the base station. The best beam selection process means a process in which the base station transmits downlink beams supported by the base station in a specific time period, and the terminal 1 f-01 checks all possible pairs of the downlink beams and the uplink beams using the uplink beams supported by the terminal, and then selects a pair having the highest signal quality.

If it is necessary for the TRP 1 f-02 or the CU 1 f-03 to receive the aperiodic CSI from the terminal 1 f-01 for a specific reason, the TRP allocates a PUCCH or PUSCH transmission resource for the aperiodic CSI to the terminal from a PDCCH to DCI, at operation 1 f-20. The terminal 1 f-01 reports the aperiodic CSI to the TRP using the PUCCH format for the aperiodic CSI configured in operation 1 f-10 and the transmission resource configured in operation 1 f-20, at operation 1 f-25. The aperiodic CSI may be transmitted n times successively or according to a determined rule. The integer n may be included in PUCCH transmission configuration related information. When reporting the aperiodic CSI, the terminal 1 f-01 may transmit it using the uplink beam with the specific direction. The uplink beam with the specific direction may be a beam determined by a random access procedure most recently performed by the terminal 1 f-01. Further, the uplink beam with the specific direction may be a beam having an uplink direction that coincides with a downlink beam direction of a serving beam by which the terminal is currently being serviced. Further, the uplink beam with the specific direction may be indicated by the network. Further, the uplink beam with the specific direction may be an uplink beam selected through a best beam pair selection process for selecting the optimum beam pair that is performed by the terminal 1 f-01 and the base station. The best beam selection process means a process in which the base station transmits downlink beams supported by the base station in a specific time period, and the terminal 1 f-01 checks all possible pairs of the downlink beams and the uplink beams using the uplink beams supported by the terminal, and then selects a pair having the highest signal quality. As an acknowledgement for acknowledging good reception of the signal in the above-described procedures, a MAC control message (MAC control information or MAC control element) may be used.

FIG. 1G is a diagram explaining a method 2 for an RRC layer of a CU and a MAC layer of a DU to configure a PUCCH and to transmit configuration information according to a (1-3)-th embodiment of the present disclosure.

Referring to FIG. 1G, the DUs or TRPs 1 d-10, 1 d-20, 1 d-30, 1 d-35, and 1 d-40 may have MAC layers. Accordingly, the TRP 1 g-02 can manage scheduling of transmission resources. In the next-generation mobile communication system, if it is necessary to configure a PUCCH of a terminal 1 g-01 for a specific reason, a CU 1 g-03 or gNB determines PUCCH transmission configuration information of the terminal 1 g-01. The PUCCH transmission configuration information determined by the CU 1 g-03 may include a PUCCH transmission period (the number of subframes for indicating a period, a system frame number indicating an activation time, and SFN), PUCCH formats (format for periodic CSI and format for aperiodic CSI), a transmission resource size, transmission beam information, reception beam information, and the number of transmissions of the aperiodic CSI. If the PUCCH transmission configuration information is determined, the CU transfers the information to the TRP, at operation 1 g-05. Further, the CU 1 g-03 configures the PUCCH transmission configuration information through direct transmission thereof to the terminal 1 g-01 as an RRC message, at operation 1 g-10.

The TRP 1 g-02 receives the PUCCH transmission configuration information from the CU 1 g-03 and determines actual transmission resource information of the PUCCH. The transmission resource information may include a system frame number indicating an activation time, SFN, RB index indicating a frequency resource, a symbol index indicating a time resource, transmission beam information, and reception beam information. If the transmission resource information is determined, the TRP 1 g-02 configures the PUCCH of the terminal 1 g-01 through transmission of the PUCCH transmission resource information to the terminal as a MAC control message (MAC control information or MAC control element), at operation 1 g-15. The terminal 1 g-01 allocated with the PUCCH transmission resource from the MAC control message may report the periodic CSI to the TRP as a PUCCH format for the periodic CSI using the PUCCH transmission configuration information received from operation 1 g-10, at operation 1 g-20. When reporting the periodic CSI, the terminal may transmit it using an uplink beam with a specific direction.

The uplink beam with the specific direction may be a beam determined by a random access procedure most recently performed by the terminal 1 g-01. Further, the uplink beam with the specific direction may be a beam having an uplink direction that coincides with a downlink beam direction of a serving beam by which the terminal 1 g-01 is currently being serviced. Further, the uplink beam with the specific direction may be indicated by the network. Further, the uplink beam with the specific direction may be an uplink beam selected through a best beam pair selection process performed by the terminal 1 g-01 and the base station. The best beam selection process means a process in which the base station transmits downlink beams supported by the base station in a specific time period, and the terminal 1 g-01 checks all possible pairs of the downlink beams and the uplink beams using the uplink beams supported by the terminal 1 g-01, and then selects a pair having the highest signal quality.

If it is necessary for the TRP 1 b-02 or the CU 1 g-03 to receive the aperiodic CSI from the terminal 1 g 01 for a specific reason, the TRP allocates a PUCCH or PUSCH transmission resource for the aperiodic CSI to the terminal 1 g-01 from a PDCCH to DCI, at operation 1 g-25. The terminal 1 g-01 reports the aperiodic CSI to the TRP using the PUCCH format for the aperiodic CSI configured in operation 1 g-10 and the transmission resource configured in operation 1 g-25, at operation 1 g-30. The aperiodic CSI may be transmitted n times successively or according to a determined rule. The integer n may be included in PUCCH transmission configuration related information. When reporting the aperiodic CSI, the terminal 1 g-01 may transmit it using the uplink beam with the specific direction.

The uplink beam with the specific direction may be a beam determined by a random access procedure most recently performed by the terminal 1 g-01. Further, the uplink beam with the specific direction may be a beam having an uplink direction that coincides with a downlink beam direction of a serving beam by which the terminal 1 g-01 is currently being serviced. Further, the uplink beam with the specific direction may be indicated by the network. Further, the uplink beam with the specific direction may be an uplink beam selected through a best beam pair selection process for selecting the optimum beam pair that is performed by the terminal 1 g-01 and the base station. The best beam selection process means a process in which the base station transmits downlink beams supported by the base station in a specific time period, and the terminal 1 g-01 checks all possible pairs of the downlink beams and the uplink beams using the uplink beams supported by the terminal 1 g-01, and then selects a pair having the highest signal quality. As an acknowledgement for acknowledging good reception of the signal in the above-described procedures, a MAC control message (MAC control information or MAC control element) may be used.

FIG. 1H is a diagram illustrating a method 3 for an RRC layer of a CU and a MAC layer of a DU to configure and transmit a PUCCH according to a (1-4)-th embodiment of the present disclosure.

Referring to FIG. 1H, the DUs or TRPs 1 d-10, 1 d-20, 1 d-30, 1 d-35, and 1 d-40 may have MAC layers. Accordingly, the TRP 1 h-02 can manage scheduling of transmission resources. In the next-generation mobile communication system, if it is necessary to configure a PUCCH of a terminal 1 h-01 for a specific reason, a CU 1 h-03 or gNB determines PUCCH transmission configuration information of the corresponding terminal. The PUCCH transmission configuration information determined by the CU 1 h-03 may include a PUCCH transmission period (the number of subframes for indicating a period, a system frame number indicating an activation time, and SFN), PUCCH formats (format for periodic CSI and format for aperiodic CSI), a transmission resource size, transmission beam information, reception beam information, and the number of transmissions of the aperiodic CSI. If the PUCCH transmission configuration information is determined, the CU 1 h-03 transfers the information to the TRP 1 h-02, at operation 1 h-05.

Then, the TRP 1 h-02 receives the PUCCH transmission configuration information from the CU 1 h-03 and determines actual transmission resource information of the PUCCH. The transmission resource information may include a system frame number indicating an activation time, SFN, RB index indicating a frequency resource, a symbol index indicating a time resource, transmission beam information, and reception beam information. If the transmission resource information is determined, the TRP 1 h-02 transfers the PUCCH transmission resource information to the CU 1 h-03, at operation 1 h-10. Then, the CU 1 h-03 configures the PUCCH transmission configuration information and the transmission resource information to the terminal 1 h-01 as an RRC control message, at operation 1 h-15. The terminal 1 h-01 in which the PUCCH is configured may report the periodic CSI to the TRP 1 h-02 as a PUCCH format for the periodic CSI using the PUCCH configuration information and the PUCCH transmission resource information, at operation 1 h-20. When reporting the periodic CSI, the terminal may transmit it using an uplink beam with a specific direction.

The uplink beam with the specific direction may be a beam determined by a random access procedure most recently performed by the terminal 1 h-01. Further, the uplink beam with the specific direction may be a beam having an uplink direction that coincides with a downlink beam direction of a serving beam by which the terminal 1 h-01 is currently being serviced. Further, the uplink beam with the specific direction may be indicated by the network. Further, the uplink beam with the specific direction may be an uplink beam selected through a best beam pair selection process performed by the terminal 1 h-01 and the base station. The best beam selection process means a process in which the base station transmits downlink beams supported by the base station in a specific time period, and the terminal 1 h-01 checks all possible pairs of the downlink beams and the uplink beams using the uplink beams supported by the terminal 1 h-01, and then selects a pair having the highest signal quality.

If it is necessary for the TRP 1 h-02 or the CU 1 h-03 to receive the aperiodic CSI from the terminal 1 h-01 for a specific reason, the TRP 1 h-02 allocates a PUCCH or PUSCH transmission resource for the aperiodic CSI to the terminal 1 h-01 from a PDCCH to DCI, at operation 1 h-25. The terminal 1 h-01 reports the aperiodic CSI to the TRP 1 h-02 using the PUCCH format for the aperiodic CSI configured in operation 1 h-10 and the transmission resource configured in operation 1 h-25, at operation 1 h-30. The aperiodic CSI may be transmitted n times successively or according to a determined rule. The integer n may be included in PUCCH transmission configuration related information. When reporting the aperiodic CSI, the terminal 1 h-01 may transmit it using the uplink beam with the specific direction.

The uplink beam with the specific direction may be a beam determined by a random access procedure most recently performed by the terminal 1 h-01. Further, the uplink beam with the specific direction may be a beam having an uplink direction that coincides with a downlink beam direction of a serving beam by which the terminal 1 h-01 is currently being serviced. Further, the uplink beam with the specific direction may be indicated by the network. Further, the uplink beam with the specific direction may be an uplink beam selected through a best beam pair selection process for selecting the optimum beam pair that is performed by the terminal 1 h-01 and the base station. The best beam selection process means a process in which the base station transmits downlink beams supported by the base station in a specific time period, and the terminal 1 h-01 checks all possible pairs of the downlink beams and the uplink beams using the uplink beams supported by the terminal 1 h-01, and then selects a pair having the highest signal quality. As an acknowledgement for acknowledging good reception of the signal in the above-described procedures, a MAC control message (MAC control information or MAC control element) may be used.

FIG. 1I is a diagram explaining the operation of a terminal according to the above-described embodiments of the present disclosure.

Referring to FIG. 1I, the terminal receives a control message, at operation 1 i-01. The control message may be determined to be one of an RRC message, a MAC control message (MAC control information or MAC control element), or DCI of a PDCCH, at operation 1 i-05.

If the control message is the RRC message or the MAC control message, the terminal first confirms transmission configuration information of a PUCCH, at operation 1 i-10. That is, the terminal confirms whether transmission of the PUCCH has currently been configured or whether transmission configuration information of the PUCCH is included in the received control message. The PUCCH transmission configuration information may include a PUCCH transmission period, PUCCH formats (format for periodic CSI and format for aperiodic CSI), a transmission resource size, transmission beam information, reception beam information, and the number of transmissions of the aperiodic CSI.

If the PUCCH transmission configuration has already been made or the PUCCH transmission configuration information is included in the received control message, the terminal proceeds to operation 1 i-15. At operation 1 i-15, the terminal confirms whether the PUCCH transmission resource information is included in the control message. The transmission resource information (time information and frequency information) may include the number of subframes indicating the period, system frame number indicating an activation time, SFN, RB index indicating a frequency resource, and a symbol index indicating a time resource.

If the PUCCH transmission resource information for the periodic CSI is confirmed at operation 1 i-15, the terminal triggers the periodic CSI, at operation 1 i-20. If the PUCCH transmission configuration information and the PUCCH transmission resource configuration information of the periodic CSI are not confirmed at operation 1 i-10 or operation 1 i-15, the terminal performs another operation corresponding to a command of the control message, at operation 1 i-25.

If the DCI is received at operation 1 i-05, the terminal confirms whether information on the PUCCH transmission resource for the aperiodic CSI is included in the DCI, at operation 1 i-30. If the information on the PUCCH transmission resource for the aperiodic CSI is included in the DCI, the terminal triggers the aperiodic CSI, at operation 1 i-35. If the information on the PUCCH transmission resource for the aperiodic CSI is not included in the DCI, the terminal performs another operation in accordance with a control command included in the DCI, at operation 1 i-25.

The operation of the terminal is not limited to the operation in FIG. 1I, but may include all the operations of the terminal as described above with reference to FIGS. 1A to 1H.

FIG. 1J is a diagram illustrating the configuration of a terminal according to an embodiment of the present disclosure.

Referring to FIG. 1J, the terminal includes a radio frequency (RF) processor 1 j-10, a baseband processor 1 j-20, a storage unit 1 j-30, and a controller 1 j-40.

The RF processor 1 j-10 performs a function for transmitting and receiving a signal through a radio channel, such as signal band conversion and amplification. That is, the RF processor 1 j-10 performs up-conversion of a baseband signal provided from the baseband processor 1 j-20 into an RF-band signal to transmit the converted signal to an antenna, and performs down-conversion of the RF-band signal received through the antenna into a baseband signal. For example, the RF processor 1 j-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), and an analog-to-digital converter (ADC). Although only one antenna is illustrated in the drawing, the terminal may be provided with a plurality of antennas. Further, the RF processor 1 j-10 may include a plurality of RF chains. Further, the RF processor 1 j-10 may perform beamforming. For the beamforming, the RF processor 1 j-10 may adjust phases and sizes of signals transmitted or received through the plurality of antennas or antenna elements. Further, the RF processor may perform multiple input multiple output (MIMO), and may receive several layers during performing of a MIMO operation. The RF processor 1 j-10 may perform reception beam sweeping through proper configuration of the plurality of antennas or antenna elements under the control of the controller, or may control the direction and the beam width of the reception beam so that the reception beam is synchronized with the transmission beam.

The baseband processor 1 j-20 performs conversion between a baseband signal and a bit string in accordance with the physical layer (PHY) standard of the system. For example, during data transmission, the baseband processor 1 j-20 generates complex symbols by encoding and modulating a transmitted bit string. Further, during data reception, the baseband processor 1 j-20 restores a received bit string by demodulating and decoding the baseband signal provided from the RF processor 1 j-10. For example, in the case of following an OFDM method, during data transmission, the baseband processor 1 j-20 generates complex symbols by encoding and modulating a transmitted bit string, performs mapping of the complex symbols on subcarriers, and then configures OFDM symbols through the inverse fast fourier transform (IFFT) operation and cyclic prefix (CP) insertion. Further, during data reception, the baseband processor 1 j-20 divides the baseband signal provided from the RF processor 1 j-10 in the unit of OFDM symbols, restores the signals mapped on the subcarriers through the fast fourier transform (FFT) operation, and then restores the received bit string through demodulation and decoding.

The baseband processor 1 j-20 and the RF processor 1 j-10 transmit and receive the signals as described above. Accordingly, the baseband processor 1 j-20 and the RF processor 1 j-10 may be called a transmitter, a receiver, a transceiver, or a communication unit. Further, in order to support different radio connection technologies, at least one of the baseband processor 1 j-20 and the RF processor 1 j-10 may include a plurality of communication modules. Further, in order to process signals of different frequency bands, at least one of the baseband processor 1 j-20 and the RF processor 1 j-10 may include different communication modules. For example, the different radio connection technologies may include an LTE network and an NR network. Further, the different frequency bands may include super high frequency (SHF) (e.g., 2.5 GHz or 5 GHz) band and millimeter wave (mmWave) (e.g., 60 GHz) band.

The storage unit 1 j-30 stores therein a basic program for an operation of the terminal, application programs, and data of configuration information. The storage unit 1 j-30 provides stored data in accordance with a request from the controller 1 j-40.

The controller 1 j-40 controls the whole operation of the terminal. For example, the controller 1 j-40 transmits and receives signals through the baseband processor 1 j-20 and the RF processor 1 j-10. Further, the controller 1 j-40 records or reads data in or from the storage unit 1 j-30. For this, the controller 1 j-40 may include at least one processor. For example, the controller 1 j-40 may include a communication processor (CP) performing a control for communication and an application processor (AP) controlling an upper layer, such as an application program, and may include a multi-connection processor 1 j-42.

FIG. 1K is a diagram illustrating the configuration of a base station in a wireless communication system according to an embodiment of the present disclosure.

Referring to FIG. 1K, the base station includes an RF processor 1 k-10, a baseband processor 1 k-20, a backhaul communication unit 1 k-30, a storage unit 1 k-40, and a controller 1 k-50.

The RF processor 1 k-10 performs a function for transmitting and receiving a signal through a radio channel, such as signal band conversion and amplification. That is, the RF processor 1 k-10 performs up-conversion of a baseband signal provided from the baseband processor 1 k-20 into an RF-band signal to transmit the converted signal to an antenna, and performs down-conversion of the RF-band signal received through the antenna into a baseband signal. For example, the RF processor 1 k-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC. Although only one antenna is illustrated in the drawing, the first connection node may be provided with a plurality of antennas. Further, the RF processor 1 k-10 may include a plurality of RF chains. Further, the RF processor 1 k-10 may perform beamforming. For the beamforming, the RF processor 1 k-10 may adjust phases and sizes of signals transmitted or received through the plurality of antennas or antenna elements. Further, the RF processor may perform down MIMO operation through transmission of one or more layers.

The baseband processor 1 k-20 performs conversion between a baseband signal and a bit string in accordance with the PHY standard of the first radio connection technology. For example, during data transmission, the baseband processor 1 k-20 generates complex symbols by encoding and modulating a transmitted bit string. Further, during data reception, the baseband processor 1 k-20 restores a received bit string by demodulating and decoding the baseband signal provided from the RF processor 1 k-10. For example, in the case of following an OFDM method, during data transmission, the baseband processor 1 k-20 generates complex symbols by encoding and modulating a transmitted bit string, performs mapping of the complex symbols on subcarriers, and then configures OFDM symbols through the IFFT operation and CP insertion. Further, during data reception, the baseband processor 1 k-20 divides the baseband signal provided from the RF processor 1 k-10 in the unit of OFDM symbols, restores the signals mapped on the subcarriers through the FFT operation, and then restores the received bit string through demodulation and decoding. The baseband processor 1 k-20 and the RF processor 1 k-10 transmit and receive the signals as described above. Accordingly, the baseband processor 1 k-20 and the RF processor 1 k-10 may be called a transmitter, a receiver, a transceiver, or a communication unit.

The backhaul communication unit 1 k-30 provides an interface for performing communication with other nodes in the network.

The storage unit 1 k-40 stores therein a basic program for an operation of the main base station, application programs, and data of configuration information. In particular, the storage unit 1 k-40 may store information on a bearer allocated to the connected terminal and the measurement result reported from the connected terminal. Further, the storage unit 1 k-40 may store information that becomes a basis of determination whether to provide or suspend a multi-connection to the terminal. Further, the storage unit 1 k-40 provides stored data in accordance with a request from the controller 1 k-50.

The controller 1 k-50 controls the whole operation of the main base station. For example, the controller 1 k-50 transmits and receives signals through the baseband processor 1 k-20 and the RF processor 1 k-10 or through the backhaul communication unit 1 k-30. Further, the controller 1 k-50 records or reads data in or from the storage unit 1 k-40. For this, the controller 1 k-50 may include at least one processor. For example, the controller 1 k-50 may include a multi-connection processor 1 k-52.

Second Embodiment

FIG. 2A is a diagram illustrating the structure of an LTE system for reference according to an embodiment of the present disclosure.

Referring to FIG. 2A, a wireless communication system is composed of several base stations 2 a-05, 2 a-10, 2 a-15, and 2 a-20, an MME 2 a-25, and a serving-gateway (S-GW) 2 a-30. UE or “terminal” 2 a-35 connects to an external network through the base stations 2 a-05, 2 a-10, 2 a-15, and 2 a-20 and the S-GW 2 a-30.

The base stations 2 a-05, 2 a-10, 2 a-15, and 2 a-20 are connection nodes in a cellular network, and provide radio connection to terminals connecting to the network. That is, in order to service users' traffics, the base stations 2 a-05, 2 a-10, 2 a-15, and 2 a-20 perform scheduling through consolidation of status information, such as a buffer state, an available transmission power state, and a channel state, of the terminals to support a connection between the terminals and a CN. The MME 2 a-25 is a device that takes charge of not only mobility management of the terminal but also various kinds of control functions. The MME is connected to the plural base stations, and the S-GW 2 a-30 is a device that provides data bearers. Further, the MME 2 a-25 and the S-GW 2 a-30 may further perform an authentication of the terminal that connects to the network and bearer management, and process packets arrived from the base stations 2 a-05, 2 a-10, 2 a-15, and 2 a-20 and packets to be transferred to the base stations 2 a-05, 2 a-10, 2 a-15, and 2 a-20.

FIG. 2B is a diagram illustrating a radio protocol structure of an LTE system according to an embodiment of the present disclosure. The radio protocol structure in the drawing may be partially different from a radio protocol structure of an NR to be defined hereafter, but the explanation thereof will be made for convenience in explaining the present disclosure.

Referring to FIG. 2B, in a terminal or an ENB, a radio protocol of an LTE system is composed of a PDCP 2 b-05 or 2 b-40, a radio link control (RLC) 2 b-10 or 2 b-35, and an MAC 2 b-15 or 2 b-30. The PDCP 2 b-05 or 2 b-40 takes charge of IP header compression/decompression operations, and the RLC 2 b-10 or 2 b-35 reconfigures a PDCP packet data unit (PDU) with a suitable size. The MAC 2 b-15 or 2 b-30 is connected to various RLC layer devices that are configured in one terminal, and performs multiplexing of RLC PDUs to a MAC PDU and demultiplexing of the RLC PDUs from the MAC PDU. Physical layer 2 b-20 or 2 b-25 performs channel coding and modulation of upper layer data and produces OFDM symbols to transmit the OFDM symbols through a radio channel, or performs demodulation and channel decoding of the OFDM symbols received through the radio channel to transfer the demodulated and decoded OFDM symbols to an upper layer. Further, the PHY uses hybrid automatic repeat request (ARQ) (HARQ) for additional error correction, and a receiving end transmits whether to receive the packet transmitted from a transmitting end with one bit. This is called HARQ ACK/negative acknowledgment (NACK) information.

Downlink HARQ ACK/NACK information against uplink transmission may be transmitted through a physical hybrid-ARQ indicator channel (PHICH), and uplink HARQ ACK/NACK information against downlink transmission may be transmitted through a PUCCH or a physical uplink shared channel (PUSCH).

Although not illustrated in the drawing, a radio resource control (RRC) layer may exist in an upper position of the PDCH layer of the terminal and the base station, and it may send and receive connection and measurement related configuration control messages for the RRC. For example, the base station may instruct the terminal to perform measurement using a message of the RRC layer, and the terminal may report the measurement result to the base station using the message of the RRC layer.

FIG. 2C is a diagram of a frame structure used in a 5G system to which the present disclosure is applied according to an embodiment of the present disclosure.

Referring to FIG. 2C, a scenario in which the 5G system operates at high frequency in order to secure a wide frequency bandwidth for a high transmission speed may be considered. However, since it is difficult to transfer a signal at high frequency, a scenario in which data is transmitted through beam generation may be considered.

Accordingly, a scenario in which a base station or a TRP 2 c-01 communicates with terminals 2 c-71, 2 c-73, 2 c-75, 2 c-77, and 2 c-79 in a cell using different beams may be considered. That is, in FIG. 2C, it is assumed that terminal 2 c-71 performs communication using beam #1 2 c-51, terminal 2 c-73 performs communication using beam #5 2 c-55, and terminals 3, 4, and 5 perform communication through beam #7 2 c-57.

In order to measure what beam the terminal communicates with the TRP through, an OSF 2 c-03 exists on time, and in the OSF, the base station transmits a RS using different beams by symbols (or through several symbols). In FIG. 2C, it is assumed that the base station transmits 12 beams #1 to #12 2 c-51 to 2 c-62, and in the OSF, different beams are swept and transmitted for each symbol 2 c-31 to 2 c-42. That is, in the OSF, respective beams are transmitted by symbols (e.g., beam #1 2 c-51 is transmitted at the first symbol 2 c-31), and the terminal can measure what beam signal transmitted in the OSF is the strongest through measurement of the OSF. In an embodiment of the present disclosure, the beam constantly transmitted in the OSF as described above is called a common beam.

In FIG. 2C, a scenario in which the corresponding OSF is repeated for 25 subframes is assumed, and the remaining 24 subframes are DSFs 2 c-05 in which general data is transmitted and received.

Accordingly, a scenario in which in accordance with the scheduling of the base station, terminals 2 c-75, 2 c-77, and 2 c-79 perform communication commonly using beam #7 2 c-11, terminal 2 c-71 performs communication using beam #1 2 c-13, and terminal 2 c-73 performs communication using beam #5 2 c-15 is assumed.

In addition, since the beam used in the DSF is a beam used for the terminal connected to the base station, data may be transmitted and received by adjusting the direction more minutely in accordance with the location of the terminal. For this, the terminal may report the strength/quality of signals transmitted from the respective beams to enable the base station to perform additional adjustment. A series of procedures for the minute adjustment as described above is called a beam refinement procedure. Through the beam refinement procedure, the base station can transmit and receive data using more optimized beam in the direction of the terminal that may differ from the direction and/or width of the beam transmitted from the OSF. In an embodiment of the present disclosure, the beam specified to the terminal through the beam refinement procedure is called a dedicated beam. It is assumed that the dedicated beam can be used only in a connected mode to be described later.

In the exemplified drawing, although the transmission beams #1 to #12 2 c-51 to 2 c-62 of the base station are illustrated, reception beams of the terminal for receiving the transmission beams of the base station (e.g., beams 2 c-81, 2 c-83, 2 c-85, and 2 c-87 of the terminal 2 c-71) may be additionally considered. In the exemplified drawing, the terminal 1 has four beams 2 c-81, 2 c-83, 2 c-85, and 2 c-87, and it performs beam sweeping in order to determine what beam has the best reception performance. In this case, if several beams cannot be simultaneously used, the optimum transmission beam of the base station and reception beam of the terminal can be found by receiving several OSFs as many as the number of reception beams through the use of one reception beam for each OSF.

FIG. 2D is a diagram explaining a message flow between a terminal and a base station in the case of using a method for selectively determining a beam to be measured in accordance with the measurement configuration proposed in an embodiment of the present disclosure.

Referring to FIG. 2D, a terminal 2 d-01 that is in an idle mode RRC IDLE camps on a corresponding base station to find a suitable cell, at operation 2 d-11, and then performs connection to the base station because of generation of data to be sent, at operation 2 d-13. In the idle mode, the terminal 2 d-01 is not connected to the network for power saving, and thus it is unable to transmit data. For data transmission, it is necessary for the terminal 2 d-01 to be shifted to a connected mode RRC_CONNECTED. Further, the term “camps” as described above means that the terminal 2 d-01 stays in a corresponding cell and receives a paging message to determine whether data is sent in the downlink. If the terminal 2 d-01 is successful in connecting to a base station 2 d-03, the state of the terminal 2 d-01 is shifted to a connected mode RRC_CONNECTED, and the terminal 2 d-01 in the connected mode can transmit/receive data to/from the base station.

Thereafter, as the terminal 2 d-01 in the connected mode moves into or out of the cell, it is necessary to command movement of the terminal so that the terminal performs transmission/reception through another beam or cell/base station. For this, the base station 2 d-03 is configured to instruct the terminal to measure a serving beam, a neighbor beam at the same transmission & reception point (TRP) of the same cell (intra-TRP), or a neighbor beam at a different TRP of the same cell (inter-TRP) or in another cell, at operation 2 d-15. The above-described measurement instruction may include one of conditions on which the terminal 2 d-01 reports the measurement result to the base station 2 d-03 if the following conditions are satisfied.

-   -   Event 1: A case where a serving beam becomes better than a         predetermined threshold value in signal strength/quality.     -   Event 2: A case where a serving beam becomes worse than a         predetermined threshold value in signal strength/quality.     -   Event 3: A case where an inter-TRP neighbor beam becomes offset         better than the best intra-TRP beam in signal strength/quality.     -   Event 4: A case where an inter-TRP neighbor beam becomes better         than a predetermined threshold value in signal strength/quality.     -   Event 5: A case where a serving beam becomes worse than a         threshold value 1 in signal strength/quality, and an inter-TRP         neighbor beam becomes better than a threshold value 2 in signal         strength/quality.

The terminal 2 d-01 that has received the configuration information as described above transmits a confirmation message indicating that the configuration information has been successfully received to the base station 2 d-03, at operation 2 d-17. For this, in the LTE, an RRC connection reconfiguration complete message may be used.

As described above with reference to FIG. 2C, if the terminal 2 d-01 is in a connected mode to perform data transmission/reception, it may use a dedicated beam other than a common beam. In an embodiment of the present disclosure, if the terminal 2 d-01 is configured with one of the above-described events, it determines what beam is selected to be measured, at operation 2 d-19. That is, a dedicated beam may be measured in accordance with the event, or even in the case where the dedicated beam is used, the common beam may be measured. The common beam may correspond to an SS block, and the dedicated block may correspond to a CSI-RS. The measurement of the common beam may be measurement based on the SS block, and the measurement of the dedicated beam may be measurement for the CSI-RS.

More specifically, if the terminal 2 d-01 measures only the signal strength/quality of a serving beam as at the events 1 and 2, it measures the common beam if it performs communication using the common beam, whereas it uses the dedicated beam if it uses the dedicated beam through a beam refinement procedure.

Further, if the terminal 2 d-01 compares a serving beam with a neighbor beam in signal strength/quality as at the event 3, it may perform measurement using the common beam even in the case where the terminal 2 d-01 uses the dedicated beam as the serving beam. This is to make a fair comparison between the serving beam and the neighbor beam because the neighbor beam that has no dedicated beam is measured using the common beam.

Further, even at an event where the terminal 2 d-01 compares a serving beam with a predetermined threshold value 1 and compares a neighbor beam with a predetermined threshold value 2 as at the event 5, and sends a report in the case where both the conditions are all satisfied, in the same manner as at the event 3, the terminal 2 d-01 performs the measurement using the common beam even in the case where the terminal 2 d-01 uses the dedicated beam as the serving beam.

If the terminal 2 d-01 measures only the signal strength/quality of a neighbor beam as at the event 4, it performs the measurement using the common beam of the corresponding neighbor beam because there is not dedicated beam for the corresponding neighbor beam.

For what event the terminal 2 d-01 compares the serving beam with the common beam may be predetermined by the terminal 2 d-01, and the base station 2 d-03 may configure the same using a message, such as an RRC message or a MAC message.

As described above, the terminal 2 d-01 selects a beam (i.e., common beam 2 d-23, common beam 2 d-25 of another base station 2 d-05, or dedicated beam 2 d-27 even in a serving beam) to be measure in accordance with a measurement event configured from the base station 2 d-03 to measure the corresponding beam, at operation 2 d-21, and if it coincides with the measurement report condition, the terminal 2 d-01 reports the measurement result to the base station 2 d-03, at operation 2 d-31. In accordance with the measurement result, the base station 2 d-03 may transmit a command to move the terminal 2 d-01 to another beam in the same TRP in the same cell, to move the terminal 2 d-01 to a beam in another TRP in the same cell, or to move the terminal to a beam of a TRP belonging to another cell. In an embodiment of the present disclosure, it is assumed that the terminal 2 d-01 can determine a cell, a TRP in the cell, and a beam identifier from a common beam transmitted by each TRP.

FIG. 2E is a diagram explaining the order of operations of a terminal according to an embodiment of the present disclosure.

Referring to FIG. 2E, in the drawing, it is assumed that a terminal in a connected mode connects to a base station/cell to transmit/receive data to/from a beam of the corresponding cell, at operation 2 e-03.

As described above, for mobility management, the terminal in a connected mode is instructed by the base station to perform measurement configuration, at operation 2 e-05. A measurement configuration instruction message may include one or more of events below, and if the following conditions are satisfied, the terminal reports the measurement result to the base station.

-   -   Event 1: A case where a serving beam becomes better than a         predetermined threshold value in signal strength/quality.     -   Event 2: A case where a serving beam becomes worse than a         predetermined threshold value in signal strength/quality.     -   Event 3: A case where an inter-TRP neighbor beam becomes offset         better than the best intra-TRP beam in signal strength/quality.     -   Event 4: A case where an inter-TRP neighbor beam becomes better         than a predetermined threshold value in signal strength/quality.     -   Event 5: A case where a serving beam becomes worse than a         threshold value 1 in signal strength/quality, and an inter-TRP         neighbor beam becomes better than a threshold value 2 in signal         strength/quality.

The terminal that has received the measurement configuration determines what event the configured measurement event is, at operation 2 e-07.

If the configured measurement event is to compare a serving beam with a predetermined threshold value in signal strength/quality like the event 1 or 2, the terminal determines whether it currently communicates with the serving cell using a common beam or a dedicated beam through a beam refinement procedure, at operation 2 e-09. If the terminal currently communicates with the serving cell using the common beam, it performs the measurement using the common beam when performing the measurement in accordance with the event, at operation 2 e-11. If the terminal currently communicates with the serving cell using the dedicated beam through the beam refinement procedure, it performs the measurement using the dedicated beam when performing the measurement in accordance with the event, at operation 2 e-13. As described above with reference to FIG. 2C, the common beam is a beam sweeping in respective directions even in a subframe, such as the OSF. Further, the dedicated beam is featured to have a different direction and/or beam width from those of the common beam, and the terminal in a connection state is featured to transmit a dedicated message for indicating what beam is to be used through the beam refinement procedure. Accordingly, the terminal determines whether to perform a measurement report through measurement of the signal strength/quality with respect to the selected serving beam, at operation 2 e-21.

If the configured measurement event is to compare a serving beam with a neighbor beam in signal strength/quality like the event 3, the terminal performs measurement using a common beam even in the case of communicating with the serving cell using a dedicate beam through a beam refinement procedure, at operation 2 e-15. The neighbor beam may be a beam of another TRP of the same cell (intra-cell inter-TRP), or a beam of another TRP of another cell (inter-cell inter-TRP). Accordingly, it is assumed that each beam includes a cell identifier and a TRP identifier. Accordingly, if the neighbor beam means a beam of another TRP of the same cell (intra-cell inter-TRP), it means that the TRP identifier becomes different, whereas if the neighbor beam means a beam of another TRP of another cell (inter-cell inter-TRP), it means that the cell identifier becomes different. Accordingly, the terminal selects the common beam with respect to the serving beam, and determines whether to perform a measurement report through measurement of signal strength/quality with respect to the serving beam and the neighbor beam, at operation 2 e-23.

If the configured measurement event is to compare a serving beam with a predetermined threshold value in signal strength/quality and to compare a neighbor beam with a predetermined threshold value in signal strength/quality like the event 5, the terminal performs measurement using a common beam even in the case of communicating with the serving cell using a dedicate beam through a beam refinement procedure, at operation 2 e-17. The neighbor beam may be a beam of another TRP of the same cell (intra-cell inter-TRP), or a beam of another TRP of another cell (inter-cell inter-TRP). Accordingly, it is assumed that each beam includes a cell identifier and a TRP identifier. Accordingly, if the neighbor beam means a beam of another TRP of the same cell (intra-cell inter-TRP), it means that the TRP identifier becomes different, whereas if the neighbor beam means a beam of another TRP of another cell (inter-cell inter-TRP), it means that the cell identifier becomes different. Accordingly, the terminal selects the common beam with respect to the serving beam, and determines whether to perform a measurement report through measurement of signal strength/quality with respect to the serving beam and the neighbor beam, at operation 2 e-23.

If it is determined to transmit the measurement result in accordance with the determination as described above, at operation 2 e-25, the terminal reports the measurement result to the base station, at operation 2 e-27. Through this, the base station can transmit a command to move the terminal to another beam in the same TRP in the same cell, to move the terminal to a beam in another TRP in the same cell, or to move the terminal to a beam of the TRP belonging to another cell.

FIG. 2F is a block diagram illustrating the configuration of a terminal according to an embodiment of the present disclosure.

Referring to FIG. 2F, the terminal includes an RF processor 2 f-10, a baseband processor 2 f-20, a storage unit 2 f-30, and a controller 2 f-40.

The RF processor 2 f-10 performs a function for transmitting and receiving a signal through a radio channel, such as signal band conversion and amplification. That is, the RF processor 2 f-10 performs up-conversion of a baseband signal provided from the baseband processor 2 f-20 into an RF-band signal to transmit the converted signal to an antenna, and performs down-conversion of the RF-band signal received through the antenna into a baseband signal. For example, the RF processor 2 f-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC. Although only one antenna is illustrated in FIG. 2F, the terminal may be provided with a plurality of antennas. Further, the RF processor 2 f-10 may include a plurality of RF chains. Further, the RF processor 2 f-10 may perform beamforming. For the beamforming, the RF processor 2 f-10 may adjust phases and sizes of signals transmitted or received through the plurality of antennas or antenna elements.

The baseband processor 2 f-20 performs conversion between a baseband signal and a bit string in accordance with the PHY standard of the system. For example, during data transmission, the baseband processor 2 f-20 generates complex symbols by encoding and modulating a transmitted bit string. Further, during data reception, the baseband processor 2 f-20 restores a received bit string by demodulating and decoding the baseband signal provided from the RF processor 2 f-10. For example, in the case of following an OFDM method, during data transmission, the baseband processor 2 f-20 generates complex symbols by encoding and modulating a transmitted bit string, performs mapping of the complex symbols on subcarriers, and then configures OFDM symbols through the IFFT operation and CP insertion. Further, during data reception, the baseband processor 2 f-20 divides the baseband signal provided from the RF processor 2 f-10 in the unit of OFDM symbols, restores the signals mapped on the subcarriers through the FFT operation, and then restores the received bit string through demodulation and decoding.

The baseband processor 2 f-20 and the RF processor 2 f-10 transmit and receive the signals as described above. Accordingly, the baseband processor 2 f-20 and the RF processor 2 f-10 may be called a transmitter, a receiver, a transceiver, or a communication unit. Further, in order to process signals of different frequency bands, at least one of the baseband processor 2 f-20 and the RF processor 2 f-10 may include different communication modules. Further, the different frequency bands may include SHF (e.g., 2.5 GHz or 5 GHz) band and millimeter wave (mm Wave) (e.g., 60 GHz) band.

The storage unit 2 f-30 stores therein a basic program for an operation of the terminal, application programs, and data of configuration information.

The controller 2 f-40 controls the whole operation of the terminal. For example, the controller 2 f-40 transmits and receives signals through the baseband processor 2 f-20 and the RF processor 2 f-10. Further, the controller 2 f-40 records or reads data in or from the storage unit 2 f-30. For this, the controller 2 f-40 may include at least one processor. For example, the controller 2 f-40 may include a CP performing a control for communication and an AP controlling an upper layer, such as an application program. In an embodiment of the present disclosure, the controller 2 f-40 includes a multi-connection processor 2 f-42. For example, the controller 2 f-40 may control the terminal to perform a procedure illustrated as the operation of the terminal as illustrated in FIG. 2F.

In an embodiment of the present disclosure, the terminal receives a message for commanding measurement from the base station after connecting to the base station. The controller that has received this determines whether a condition to transmit a measurement report to the base station is satisfied through measurement of the beam to be measured in accordance with the measurement event configured from the base station. If the condition is satisfied, the controller generates a message including the measurement result and transmits the generated message to the base station through the baseband processor and the RF processor.

Third Embodiment

FIG. 3A is a diagram explaining a multi-connectivity operation scenario in a next-generation mobile communication system according to an embodiment of the present disclosure.

Referring to FIG. 3A, a radio access network of a next-generation mobile communication system is composed of an NR NB 3 a-15 and an NR CN 3 a-05. A user terminal (NR UE) 3 a-20 connects to an external network through the NR NB 3 a-15 and the NR CN 3 a-05.

Referring to FIG. 3A, the NR NB 3 a-15 corresponds to an eNB of the existing LTE system. The NR NB may be connected to the NR UE 3 a-20 through a radio channel, and thus can provide a more superior service than the service of the existing node B. Since all user traffics are serviced through shared channels, a device that performs scheduling through consolidation of status information, such as a buffer state, an available transmission power state, and a channel state, of each UE is necessary, and the NR NB 3 a-15 takes charge of this. One NR NB generally controls plural cells. In order to implement ultrahigh-speed data transmission as compared with the existing LTE, the NR NB may have a bandwidth that is equal to or higher than the existing maximum bandwidth, and a beamforming technology may be additionally grafted in consideration of OFDM as a radio connection technology. Further, an AMC method that determines a modulation scheme and a channel coding rate to match the channel state of the terminal is applied to the NR NB. The NR NB 3 a-15 performs mobility support, bearer configuration, and QoS configuration. The NR CN is a device that takes charge of not only terminal mobility management but also various kinds of control functions, and is connected to a plurality of base stations. Further, the next-generation mobile communication system may interlock with the existing LTE system, and the NR CN is connected to an MME 3 a-10 through a network interface. The MME is connected to an eNB 3 a-25 that is the existing base station. The terminal may be simultaneously connected to the NR NB and the eNB to receive services. This is called multi-connectivity. The multi-connectivity is defined as follows.

Mode of operation whereby a multiple Rx/Tx UE in the connected mode is configured to utilize radio resources amongst E-UTRA and/or NR provided by multiple distinct schedulers connected via non-ideal backhaul.

As an example of one service scenario, a multi-connected terminal may receive a super high-speed data transmission service through the NR, and may receive a VoLTE (voice) service through the LTE.

FIG. 3B is a diagram explaining a terminal having a plurality of RF chains to support multi-connectivity according to an embodiment of the present disclosure. In order to support multi-connectivity, a plurality of RF chains are necessary.

Referring to FIG. 3B, the terminal has one RF chain composed of an RX chain 3 b-05 and a TX chain 3 b-10 supporting the NR and one RF chain composed of an RX chain 3 b-15 and a TX chain 3 b-20 supporting the LTE. The terminal having the plurality of RF chains can simultaneously perform data transmission/reception with the NR and the LTE. However, such a structure may increase power consumption of the terminal due to a large number of RF chains, and there is no room for saving in material cost. In the case of a cheap terminal, such cost increase may cause multi-connectivity support to be not possible. Further, intra-device interference may occur between RX and TX chains. This is called in-device coexistence (IDC) interference. For example, a signal that is radiated from the TX chain may be input to the RX chain of the NR to become an interference signal of the NR.

FIG. 3C is a diagram explaining application of a TDM method to support multi-connectivity.

Referring to FIG. 3C, one method to overcome the drawback of the multi-connectivity using a plurality of RF chains as described above is to apply a TDM method to transmit/receive data only with one system at one moment in a state where a single RF chain is utilized. The single RF chain means reduction of the power consumption and the material cost in the terminal. Further, by the TDM method, IDC interference can be excluded. For example, in the case where NR is used in frequency F1 and LTE is used in frequency F2, the terminal may transmit/receive data to/from the NR at a specific time period t1 3 c-05, and may transmit/receive data to/from the LTE at a specific time period t3 3 c-15 after a predetermined RF conversion time t2 3 c-10. In order for a single RF chain to control a predetermined frequency band, a predetermined time is required. Accordingly, data transmission/reception is not performed during the above-described time period.

FIG. 3D is a diagram explaining a terminal having a single RF chain to apply a TDM method according to an embodiment of the present disclosure.

Referring to FIG. 3D, a terminal has a single RF chain composed of one RX chain 3 d-05 and one TX chain 3 d-10. For a specific time period, the RF chain of the terminal is configured as a frequency being used by the NR or LTE. Further, for a specific time period, the RX chain may be configured as an NR frequency (LTE frequency), and the TX chain may be configured as an LTE frequency (NR frequency).

FIG. 3E is a diagram explaining a terminal having a single TX chain and plural RX chains to apply a TDM method according to an embodiment of the present disclosure.

Referring to FIG. 3E, the terminal has a plurality of RX chains 3 e-05 and 3 e-10 and one TX chain 3 e-15. The terminal can simultaneously receive data from the NR and the LTE, but can transmit data to the NR or the LTE only for a specific time period. The above-described structure has low efficiency from the viewpoint of power consumption and cost, but may have an advantage from the viewpoint of complexity.

FIG. 3F is a diagram explaining a (3-1)-th embodiment to configure TDM type multi-connectivity according to an embodiment of the present disclosure.

Referring to FIG. 3F, a terminal 3 f-05 camps on a first base station 3 f-10. In this case, the first base station 3 f-10 serves as a master that triggers a TDM operation. The first base station 3 f-10 may be either an NR NB or an eNB. The first base station 3 f-10 notifies the terminal 3 f-05 whether the first base station 3 f-10 itself supports the TDM operation, at operation 3 f-20. The terminal 3 f-05 notifies the first base station 3 f-10 whether the terminal 3 f-05 itself supports the TDM operation, at operation 3 f-30. A second base station 3 f-15 notifies the first base station 3 f-10 whether the second base station 3 f-15 itself supports the TDM operation, at operation 3 f-25. The first base station 3 f-10 determines whether to configure the TDM operation in accordance with a service or QoS being provided to the terminal 3 f-05, at operation 3 f-35. Further, the terminal 3 f-05 determines whether the TDM operation is necessary in accordance with the service or QoS to be provided to the terminal 3 f-05 itself, and may request the first base station to provide the TDM operation, at operation 3 f-40.

If it is determined to configure the TDM operation in accordance with the determination of the first base station 3 f-10 or the terminal request, the first base station 3 f-10 provides configuration information related to the TDM operation to the terminal 3 f-05, at operation 3 f-45. The configuration information includes at least information on a TDM pattern. The TDM pattern is time information in which the terminal 3 f-05 can transmit/receive data at an NR or LTE frequency. The information may be provided in the form of a bit map or may be provided as time period information for staying at a specific frequency, period, and offset information. If the information is provided in the form of a bit map, each bit is used to indicate a frequency at which the terminal 3 f-05 transmits/receives data for a specific unit time. The specific unit time may be configured. If the information is provided as the time period information for staying at a specific frequency, period, and offset information, a time point when data is to be transmitted or received at a specific frequency is calculated using the offset information, and data is transmitted or received for the indicated time period at the frequency using the time period information for staying at the specific frequency. The time period arrives with a specific period. The terminal 3 f-05 that has received the TDM configuration information operates a specific timer, at operation 3 f-50. Until the specific timer expires, the terminal should complete RRC connection establishment with the second base station 3 f-15.

During the time when the specific timer operates, the RF chain of the terminal should be configured as the frequency used by the second base station 3 f-15, at operation 3 f-55. During the time period, the terminal 3 f-05 receives system information from the second base station 3 f-15, at operation 3 f-60, and performs random access, at operation 3 f-65. Further, during the time period, the terminal provides the TDM configuration information provided from the first base station 3 f-10 to the second base station 3 f-15. If the RRC connection establishment with the second base station 3 f-15 is completed, the terminal 3 f-05 starts the TDM operation at the specific time, at operation 3 f-70. If the RRC connection establishment is not successfully completed until the timer expires, at operation 3 f-75, the terminal 3 f-05 cannot start the TDM operation, and in this case, the terminal 3 f-05 notifies the first base station 3 f-10 of such a failure using a specific message, at operation 3 f-80. The specific time when the TDM operation starts should be known to the terminal 3 f-05, the first base station 3 f-10, and the second base station 3 f-15 in all. Accordingly, a method for specifying this is necessary.

-   -   Method 1: A method in which the terminal 3 f-05 notifies the NR         or LTE of the time to start the TDM operation using the specific         message of operation 3 f-80. If the RRC connection establishment         with the second base station 3 f-15 is completed, the terminal 3         f-05 notifies the first base station of this using L1 signaling,         MAC CE, or RRC message. The second base station 3 f-15 can         implicitly grasp the TDM operation time based on the random         access performance completion. Further, like the first base         station 3 f-10, the terminal 3 f-05 may notify the second base         station 3 f-15 of this using the L1 signaling, MAC CE, or RRC         message.     -   Method 2: A method in which the first base station 3 f-10         implicitly starts the TDM operation. The first base station 3         f-10 starts the TDM operation using a self-timer without         receiving any message from the terminal 3 f-05. The timer will         start after the TDM configuration information is provided to the         terminal 3 f-05, and may have the configuration value that is         the same as or is similar to the configuration value of the         timer. The second base station 3 f-15 can also implicitly grasp         the TDM operation time based on the random access performance         completion.

If the TDM operation starts, the terminal 3 f-05 performs data transmission/reception through conversion of the NR and LTE frequencies using the TDM pattern information, at operations 3 f-85 and 3 f-90.

FIG. 3G is a diagram explaining the operation of a terminal according to the first embodiment of the present disclosure.

Referring to FIG. 3G, at operation 3 g-05, the terminal exchanges TDM support capability with the first base station on which the terminal camps. At operation 3 g-10, the terminal requests the TDM operation from the first base station in accordance with the kind of service to be provided to the terminal itself or QoS. At operation 3 g-15, the terminal receives the TDM configuration information from the first base station. The configuration information includes TDM pattern information. At operation 3 g-20, the terminal receives system information from the second base station at operation 3 g-25, and at operation 3 g-30, the terminal performs a random access process. At operation 3 g-35, the terminal transmits the whole or a part of the TDM configuration information provided from the first base station to the second base station. The transmitted configuration information includes at least the TDM pattern information. At operation 3 g-40, the terminal performs TDM operation with the first and second base stations at a specific time.

FIG. 3H is a diagram explaining the operation of a first base station according to the first embodiment of the present disclosure.

Referring to FIG. 3H, at operation 3 h-05, the first base station exchanges TDM support capability with the terminal. At operation 3 h-10, the first base station determines the TDM operation in accordance with the kind of service to be provided to the terminal or QoS and the service provider/network policy. At operation 3 h-15, the first base station transmits the TDM configuration information to the terminal. At operation 3 h-20, the first base station performs the TDM operation with the terminal at a specific time.

FIG. 3I is a diagram explaining a second embodiment to configure TDM type multi-connectivity according to an embodiment of the present disclosure.

Referring to FIG. 3I, a terminal 3 i-05 camps on a first base station 3 i-10. In this case, the first base station serves as a master that triggers a TDM operation. The first base station may be either an NR NB or an eNB. The first base station 3 i-10 notifies the terminal 3 i-05 whether the first base station 3 i-10 itself supports the TDM operation, at operation 3 i-20. The terminal 3 i-05 notifies the first base station 3 i-10 whether the terminal 3 i-05 itself supports the TDM operation, at operation 3 i-30. A second base station 3 i-15 notifies the first base station 3 i-10 whether the second base station 3 i-15 itself supports the TDM operation, at operation 3 i-25. The first base station ei-10 determines whether to configure the TDM operation in accordance with a service or QoS being provided to the terminal 3 i-05, at operation 3 i-35. Further, the terminal determines whether the TDM operation is necessary in accordance with the service or QoS to be provided to the terminal 3 i-05 itself, and may request the first base station 3 i-10 to provide the TDM operation, at operation 3 i-40. If it is determined to configure the TDM operation in accordance with the determination of the first base station 3 i-10 or the terminal request, the first base station 3 i-10 requests the second base station 3 i-15 to provide the TDM operation using a message including configuration information related to the TDM operation, at operation 3 i-45. The second base station 3 i-15 transmits a response message to the first base station 3 i-10, at operation 3 i-50. The first base station 3 i-10 that has received an acceptance response message from the second base station 3 i-15 provides the configuration information related to the TDM operation to the terminal 3 i-05, at operation 3 i-55. The configuration information includes at least TDM pattern information. The TDM pattern is time information in which the terminal 3 i-05 can transmit/receive data at an NR or LTE frequency. The information may be provided in the form of a bit map or may be provided as time period information for staying at a specific frequency, period, and offset information. If the information is provided in the form of a bit map, each bit is used to indicate a frequency at which the terminal 3 i-05 transmits/receives data for a specific unit time. The specific unit time may be configured. If the information is provided as the time period information for staying at a specific frequency, period, and offset information, a time point when data is to be transmitted or received at a specific frequency is calculated using the offset information, and data is transmitted or received for the indicated time period at the frequency using the time period information for staying at the specific frequency. The time period arrives with a specific period. The terminal 3 i-05 that has received the TDM configuration information operates a specific timer, at operation 3 i-60. Until the specific timer expires, the terminal 3 i-05 should complete a connection with the second base station. During the time when the specific timer operates, the RF chain of the terminal 3 i-05 should be configured as the frequency used by the second base station 3 i-15, at operation 3 i-70. During the time period, the terminal 3 i-05 receives system information from the second base station 3 i-15, at operation 3 i-65, and performs a random access process, at operation 3 i-75. The system information of the second base station 3 i-15 may be transferred to the terminal 3 i-05 through an RRC connection reconfiguration message at operation 3 i-55. When receiving a TDM response at operation 3 i-50 from the second base station 3 i-15, the first base station 3 i-10 may be provided with the system information of the second base station 3 i-15 together. Further, during the time period, the terminal 3 i-05 provides the TDM configuration information provided from the first base station 3 i-10 to the second base station 3 i-15, at operation 3 i-80. If the second base station 3 i-15 successfully receives an RRC connection reconfiguration complete message from the terminal 3 i-05, a connection to the second base station 3 i-15 is completed, and the TDM operation starts at a specific time. If the connection is not successfully completed until the timer expires, at operation 3 i-85, the terminal 3 i-05 cannot start the TDM operation, and in this case, the terminal 3 i-05 notifies the first base station 3 i-10 of a failure using a specific message, at operation 3 i-90. The specific time when the TDM operation starts should be known to the terminal 3 i-05, the first base station 3 i-10, and the second base station 3 i-15 in all. A method for specifying has been described.

If the TDM operation starts, the terminal 3 i-05 performs data transmission/reception through conversion of the NR and LTE frequencies using the TDM pattern information, at operations 3 i-95 and 3 i-100.

In the case of the structure illustrated in FIG. 3D, the terminal 3 i-05 may perform the TDM operation with respect to the downlink and the uplink. In the case of the structure illustrated in FIG. 3E, the terminal 3 i-05 may perform the TDM operation when transmitting the uplink signal and data with respect to the downlink.

The terminal 3 i-05 can be doubly linked to the first base station 3 i-10 and the second base station 3 i-15, and in the case where the first base station 3 i-10 is an LTE base station and the second base station 3 i-15 is an NR base station, it may correspond to an EN-DC.

FIG. 3J is a diagram explaining the operation of a first base station according to the (3-2)-th embodiment of the present disclosure.

Referring to FIG. 3J, at operation 3 j-05, the first base station exchanges TDM support capability with the terminal. At operation 3 j-10, the first base station determines the TDM operation in accordance with the kind of service to be provided to the terminal or QoS and the service provider/network policy. At operation 3 j-15, the first base station requests the second base station to provide the TDM operation. At operation 3 j-20, the first base station receives an acceptance response message from the second base station. At operation 3 j-25, the first base station transmits the TDM configuration information to the terminal. At operation 3 j-30, the first base station performs the TDM operation with the terminal at a specific time.

FIG. 3K is a diagram explaining a scenario of releasing a TDM method according to an embodiment of the present disclosure.

Referring to FIG. 3K, if a specific event occurs, a terminal that performs a TDM operation may suspend this. In an embodiment of the present disclosure, if emergency disaster information, such as earthquake and tsunami warning system (ETWS)/commercial mobile alert system (CMAS), is transmitted, the TDM operation being performed is suspended or released, at 3 k-15, and the emergency disaster information is preferentially received from a system that provides the ETWS/CMAS. Generally, considering the importance of the matter, the terminal should complete the reception of the emergency disaster information as soon as possible. However, in the case of maintaining the TDM operation, it may take time to complete the reception of the emergency disaster information. For example, in the case where the emergency disaster information is provided only in an NR system, switching to an LTE system means that it takes time that much until the reception of the emergency disaster information is completed. Even in the case where both the NR and LTE systems provide the emergency disaster information, emergency disaster messages transmitted from the respective systems have different formats, and thus it is advantageous to receive the emergency disaster information only in a specific system from the viewpoint of time delay. The terminal receives a paging message indicating that an emergency disaster message is being transmitted from the NR or LTE system. The terminal that has received the paging message disregards the configured TDM operation, and receives system information including the emergency disaster message being broadcast by the system that has transmitted the paging message. The configured TDM operation is not performed until the emergency disaster message has been successfully received.

Further, in an embodiment of the present disclosure, the terminal may suspend or release the configured TDM operation with respect to a specific system if it

-   -   performs reestablishment, or     -   handover, or     -   if an RLF occurs.

If the RLF occurs, the terminal operation differs depending on whether the base station in which the RLF has occurred is a mater or a slave. If the RLF occurs in the master base station, the terminal suspends or releases the TDM operation, and performs a reestablishment operation. If the RLF occurs in the slave base station, the terminal may perform the reestablishment operation or may release the connection at all. In the case of performing the reestablishment operation, the operation is performed at the frequency of the system in which the RLF has occurred, and during performing the operation, the TDM operation is not performed. This is to maximize the success rate of the reestablishment.

Even in the case where the handover is performed, the RF chain is fixed to the frequency of the system in which the handover is performed. That is, the TDM operation is suspended or is released. This is also to maximize the success rate of the handover.

In an embodiment of the present disclosure, if the above-described reason occurs in the terminal that performs the TDM operation, the terminal may release or suspend the TDM operation, and such an operation may be applied to all of the TDM operation for uplink transmission of the terminal and the TDM operation for downlink reception of the terminal.

FIG. 3L is a block diagram illustrating the internal structure of a terminal according to an embodiment of the present disclosure.

Referring to FIG. 3L, the terminal includes an RF processor 3 l-10, a baseband processor 3 l-20, a storage unit 3 l-30, and a controller 3 l-40.

The RF processor 3 l-10 performs a function for transmitting and receiving a signal through a radio channel, such as signal band conversion and amplification. That is, the RF processor 3 l-10 performs up-conversion of a baseband signal provided from the baseband processor 3 l-20 into an RF-band signal to transmit the converted signal to an antenna, and performs down-conversion of the RF-band signal received through the antenna into a baseband signal. For example, the RF processor 3 l-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC. Although only one antenna is illustrated in the drawing, the terminal may be provided with a plurality of antennas. Further, the RF processor 3 l-10 may include a plurality of RF chains. Further, the RF processor 3 l-10 may perform beamforming. For the beamforming, the RF processor 3 l-10 may adjust phases and sizes of signals transmitted or received through the plurality of antennas or antenna elements. Further, the RF processor may perform MIMO, and may receive several layers during performing of a MIMO operation.

The baseband processor 3 l-20 performs conversion between a baseband signal and a bit string in accordance with the PHY standard of the system. For example, during data transmission, the baseband processor 3 l-20 generates complex symbols by encoding and modulating a transmitted bit string. Further, during data reception, the baseband processor 3 l-20 restores a received bit string by demodulating and decoding the baseband signal provided from the RF processor 3 l-10. For example, in the case of following an OFDM method, during data transmission, the baseband processor 3 l-20 generates complex symbols by encoding and modulating a transmitted bit string, performs mapping of the complex symbols on subcarriers, and then configures OFDM symbols through IFFT operation and CP insertion. Further, during data reception, the baseband processor 3 l-20 divides the baseband signal provided from the RF processor 3 l-20 in the unit of OFDM symbols, restores the signals mapped on the subcarriers through the FFT operation, and then restores the received bit string through demodulation and decoding.

The baseband processor 3 l-20 and the RF processor 3 l-10 transmit and receive the signals as described above. Accordingly, the baseband processor 3 l-20 and the RF processor 3 l-10 may be called a transmitter, a receiver, a transceiver, or a communication unit. Further, in order to support different radio connection technologies, at least one of the baseband processor 3 l-20 and the RF processor 3 l-10 may include a plurality of communication modules. Further, in order to process signals of different frequency bands, at least one of the baseband processor 3 l-20 and the RF processor 3 l-10 may include different communication modules. For example, the different radio connection technologies may include an LTE network and an NR network. Further, the different frequency bands may include SHF (e.g., 2·NR Hz or NR Hz) band and millimeter wave (mmWave) (e.g., 60 GHz) band.

The storage unit 3 l-30 stores therein a basic program for an operation of the terminal, application programs, and data of configuration information. In particular, the storage unit 3 l-30 may store information related to a second connection node that performs wireless communication using the second radio connection technology. Further, the storage unit 3 l-30 provides stored data in accordance with a request from the controller 3 l-40.

The controller 3 l-40 controls the whole operation of the terminal. For example, the controller 3 l-40 transmits and receives signals through the baseband processor 3 l-20 and the RF processor 3 l-10. Further, the controller 3 l-40 records or reads data in or from the storage unit 3 l-30. For this, the controller 3 l-40 may include at least one processor. For example, the controller 3 l-40 may include a CP performing a control for communication and an AP controlling an upper layer, such as an application program. The controller 3 l-40 may include a multi-connection processor 3 l-42.

FIG. 3M is a block diagram illustrating the configuration of a base station according to an embodiment of the present disclosure.

Referring to FIG. 3M, the base station includes an RF processor 3 m-10, a baseband processor 3 m-20, a backhaul communication unit 3 m-30, a storage unit 3 m-40, and a controller 3 m-50.

The RF processor 3 m-10 performs a function for transmitting and receiving a signal through a radio channel, such as signal band conversion and amplification. That is, the RF processor 3 m-10 performs up-conversion of a baseband signal provided from the baseband processor 3 m-20 into an RF-band signal to transmit the converted signal to an antenna, and performs down-conversion of the RF-band signal received through the antenna into a baseband signal. For example, the RF processor 3 m-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC. Although only one antenna is illustrated in the drawing, the first connection node may be provided with a plurality of antennas. Further, the RF processor 3 m-10 may include a plurality of RF chains. Further, the RF processor 3 m-10 may perform beamforming. For the beamforming, the RF processor 3 m-10 may adjust phases and sizes of signals transmitted or received through the plurality of antennas or antenna elements. Further, the RF processor may perform down MIMO operation through transmission of one or more layers.

The baseband processor 3 m-20 performs conversion between a baseband signal and a bit string in accordance with the PHY standard of the first radio connection technology. For example, during data transmission, the baseband processor 3 m-20 generates complex symbols by encoding and modulating a transmitted bit string. Further, during data reception, the baseband processor 3 m-20 restores a received bit string by demodulating and decoding the baseband signal provided from the RF processor 3 m-10. For example, in the case of following an OFDM method, during data transmission, the baseband processor 3 m-20 generates complex symbols by encoding and modulating a transmitted bit string, performs mapping of the complex symbols on subcarriers, and then configures OFDM symbols through the IFFT operation and CP insertion. Further, during data reception, the baseband processor 3 m-20 divides the baseband signal provided from the RF processor 3 m-10 in the unit of OFDM symbols, restores the signals mapped on the subcarriers through the FFT operation, and then restores the received bit string through demodulation and decoding. The baseband processor 3 m-20 and the RF processor 3 m-10 transmit and receive the signals as described above. Accordingly, the baseband processor 3 m-20 and the RF processor 3 m-10 may be called a transmitter, a receiver, a transceiver, or a communication unit.

The backhaul communication unit 3 m-30 provides an interface for performing communication with other nodes in the network. That is, the backhaul communication unit 3 m-30 converts a bit string that is transmitted from the master base station to another node, for example, an auxiliary base station or a CN, into a physical signal, and converts a physical signal that is received from the other node into a bit string.

The storage unit 3 m-40 stores therein a basic program for an operation of the master base station, application programs, and data of configuration information. In particular, the storage unit 3 m-40 may store information on a bearer allocated to the connected terminal and the measurement result reported from the connected terminal. Further, the storage unit 3 m-40 may store information that becomes a basis of determination whether to provide or suspend a multi-connection to the terminal. Further, the storage unit 3 m-40 provides stored data in accordance with a request from the controller 3 m-50.

The controller 3 m-50 controls the whole operation of the master base station. For example, the controller 3 m-50 transmits and receives signals through the baseband processor 3 m-20 and the RF processor 3 m-10 or through the backhaul communication unit 3 m-30. Further, the controller 3 m-50 records or reads data in or from the storage unit 3 m-40. For this, the controller 3 m-50 may include at least one processor. The controller 3 m-50 may include a multi-connection processor 3 m-52.

Fourth Embodiment

FIG. 4A is a diagram illustrating the structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

Referring to FIG. 4A, a radio access network of a next-generation mobile communication system is composed of a new radio node B (hereinafter referred to as “NR NB”) 4 a-10 and an NR CN 4 a-05. A user terminal (“NR UE” or “terminal”) 4 a-15 connects to an external network through the NR NB 4 a-10 and the NR CN 4 a-05.

In FIG. 4A, the NR NB 4 a-10 corresponds to an eNB of the existing LTE system. The NR NB may be connected to the NR UE 4 a-15 through a radio channel, and thus can provide a more superior service than the service of the existing node B. Since all user traffics are serviced through shared channels, a device that performs scheduling through consolidation of status information, such as a buffer state, an available transmission power state, and a channel state, of each UE is necessary, and the NR NB 4 a-10 takes charge of this. One NR NB generally controls plural cells. In order to implement ultrahigh-speed data transmission as compared with the existing LTE, the NR NB may have a bandwidth that is equal to or higher than the existing maximum bandwidth, and a beamforming technology may be additionally grafted in consideration of OFDM as a radio connection technology. Further, an AMC method that determines a modulation scheme and a channel coding rate to match the channel state of the terminal is applied to the NR NB. The NR CN 4 a-05 performs mobility support, bearer configuration, and QoS configuration. The NR CN is a device that takes charge of not only terminal mobility management but also various kinds of control functions, and is connected to a plurality of base stations. Further, the next-generation mobile communication system may interlock with the existing LTE system, and the NR CN is connected to an MME 4 a-25 through a network interface. The MME is connected to an eNB 4 a-30 that is the existing base station.

FIG. 4B is a diagram of a frame structure used by an NR system to which the present disclosure is applied according to an embodiment of the present disclosure.

Referring to FIG. 4B, a scenario in which the NR system operates at high frequency in order to secure a wide frequency bandwidth for a high transmission speed may be considered. However, since it is difficult to transfer a signal at high frequency, a scenario in which data is transmitted through beam generation may be considered.

Accordingly, a scenario in which a base station or a TRP 4 b-01 communicates with terminals 4 b-71, 4 b-73, 4 b-75, 4 b-77, and 4 b-79 in a cell using different beams may be considered. That is, in FIG. 4B, it is assumed that terminal 4 b-71 performs communication using beam #1 4 b-51, terminal 4 b-73 performs communication using beam #5 4 b-55, and terminals 3, 4, and 5 perform communication through beam #7 4 b-57.

In order to measure what beam the terminal communicates with the TRP through, an OSF 4 b-03 exists on time, and in the OSF, the base station transmits a RS using different beams by symbols (or through several symbols). Beam index values for discriminating the respective beams from the RS may be derived. In FIG. 4B, it is assumed that the base station transmits 12 beams #1 to #12 4 b-51 to 4 b-62, and in the OSF, different beams are swept and transmitted for each symbol 4 b-31 to 4 b-42. That is, in the OSF, respective beams are transmitted by symbols (e.g., beam #1 4 b-51 is transmitted at the first symbol 4 b-31), and the terminal can measure what beam signal transmitted in the OSF is the strongest through measurement of the OSF.

In FIG. 4B, a scenario in which the corresponding OSF is repeated for 25 subframes is assumed, and the remaining 24 subframes are DSFs 4 b-05 in which general data is transmitted and received.

Accordingly, a scenario, in which in accordance with the scheduling of the base station, terminals 4 b-75, 4 b-77, and 4 b-79 perform communication commonly using beam #7 4 b-11, terminal 4 b-71 performs communication using beam #1 4 b-13, and terminal 4 b-73 performs communication using beam #5 4 b-15 is assumed.

In the exemplified drawing, although the transmission beams #1 to #12 4 b-51 to 4 b-62 of the base station are illustrated, reception beams of the terminal for receiving the transmission beams of the base station (e.g., beams 4 b-81, 4 b-83, 4 b-85, and 4 b-87 of the terminal 4 b-71) may be additionally considered. In the exemplified drawing, the terminal 1 has four beams 4 b-81, 4 b-83, 4 b-85, and 4 b-87, and it performs beam sweeping in order to determine what beam has the best reception performance. In this case, if several beams cannot be simultaneously used, the optimum transmission beam of the base station and reception beam of the terminal can be found by receiving several OSFs as many as the number of reception beams through the use of one reception beam for each OSF.

FIG. 4C is a diagram explaining a radio link monitoring (RLM) operation in an LTE system according to an embodiment of the present disclosure.

Referring to FIG. 4C, a PHY 4 c-10 measures downlink signal quality based on a cell specific reference signal (CRS). The signal quality means reference signal received power (RSRP) or reference signal received quality (RSRQ). The measured value is compared with a specific threshold value Qout. The threshold value is a signal quality value that satisfies a specific block error rate (BLER) of a PDCCH. If the measured value is not higher than the threshold value, the PHY transmits an “out-of-sync” indicator to an upper (“higher”) layer 4 c-05. The relationship between the threshold value and the BLER is influenced by the terminal performance, and thus it is derived through terminal implementation.

FIG. 4D is a diagram explaining a radio link failure (RLF) operation in an LTE system according to an embodiment of the present disclosure.

Referring to FIG. 4D, a PHY of a terminal compares a measured CRS signal quality with Qout in a specific period 4 d-05. If an upper layer receives an “out-of-sync” indicator N310 times from the physical layer, a T310 timer 4 d-20 operates, at 4 d-15. If an “in-sync” indicator is reported by the PHY N311 times before the T310 timer expires, the T310 timer is suspended. In contrast, if the T310 timer expires, an RLF is declared, at 4 d-25. Thereafter, the terminal initializes a reestablishment process, and operates a T311 timer 4 d-30. If the terminal finds a suitable cell, it suspends the T311 timer, and operates the T301 timer 4 d-40, at 4 d-35. The T301 timer is suspended if the terminal receives an RRC connection reestablishment message from a base station. If the T311 or T301 timer expires, the terminal is shifted to a standby mode, at 4 d-45. The values of N310, N311, T310, T311, and T301 are provided from a network.

FIG. 4E is a diagram conceptually explaining an RLF operation in a next-generation mobile communication system according to an embodiment of the present disclosure.

Referring to FIG. 4E, even the next-generation mobile communication system may have an RLF process that is similar to that of the existing LTE. Conceptually, if a state where the downlink signal quality measured by the terminal is worse than the specific threshold value, at 4 e-05, Qout continues for a specific time 4 e-10, the RFL is declared, at 4 e-15. After the RLF is declared, a reestablishment process for connection recovery is performed, at 4 e-20. If the reestablishment process is not successfully performed, the terminal is shifted to a standby mode, at 4 e-25.

FIG. 4F is a diagram explaining a serving beam and a beam group in RLM/RLF in a next-generation mobile communication system according to an embodiment of the present disclosure.

Referring to FIG. 4F, one TRP 4 f-01 is composed of one or more beams 4 f-51 to 4 f-62. A downlink serving beam 4 f-55 is a downlink beam of a TRP that is used when the TRP transmits/receives data to/from a terminal. In general, the width of a beam antenna is very narrow, and in the case of a moving terminal, the measured signal quality of a serving beam is abruptly changed. In contrast, the serving beam can be easily changed to a neighbor beam in the same TRP. For an RLM operation, only a RS provided by the serving beam may be measured and compared with a specific threshold value Qout, but it is insufficient to declare an RLF based on this. This is because the terminal can recover the radio connection relatively easily through sufficient change of the serving beam to another beam in the same TRP. Accordingly, in the case of performing the RLM operation, it is necessary to consider not only the signal quality of the serving beam but also the signal quality of the neighbor beam in the same TRP.

In an embodiment of the present disclosure, it is featured that the signal quality of a specific beam group 4 f-63 in the same TRP is additionally considered during the RLM operation. The beam group is composed of the whole or partial beams in the same TRP, and various composing method may be used. For example, a beam that belongs to the beam group may be defined as,

-   -   a beam capable of providing the constant signal quality to the         terminal in the same TRP,     -   a beam that is adjacent to the current serving beam of the         terminal in the same TRP, or     -   all beams in the same TRP.

In an embodiment of the present disclosure, it is featured that during performing of the RLM operation, the terminal considers not only the signal quality of the serving beam but also the collective signal quality of a specific beam group in the same TRP (intra-TRP). The collective signal quality of the beam group may be,

-   -   the best signal quality among signal qualities of beams that         belong to the group,     -   an average of signal qualities of n upper beams in the group,     -   total sum of signal qualities of beams that belong to the group,     -   an average value of signal qualities of beams that belong to the         group, or     -   a weighted sum of signal qualities of beams after giving         predetermined weights to the signal qualities.

If the collective signal quality of the beam group is higher than a specific threshold value although the signal quality of the serving beam is not good, it is preferable to perform a radio link recovery operation for changing the serving beam as another beam in the same TRP (one beam that belongs to the beam group) other than declaring the RLF.

FIG. 4G is a diagram explaining an RLM operation according to an embodiment of the present disclosure.

Referring to FIG. 4G, a PHY 4 g-10 checks whether the signal quality of a serving beam and the collective signal quality of a specific beam group are better than different threshold values, respectively. The PHY periodically reports the results to an upper (“higher”) layer 4 g-05. If the signal quality of the serving beam is lower than a first threshold value Qout, and the collective signal quality of the specific beam group is higher than a second threshold value Qout (beam group), the PHY reports a “radio link recovery” indicator to the upper layer. If the upper layer firstly receives the “radio link recovery” indicator as a report, a first timer operates, and if the first timer expires, the terminal performs a first process. During the first process, the terminal performs an operation to change the serving beam to another beam in the same TRP. If the signal quality of the serving beam becomes better than the first threshold value, or the signal quality of the specific beam group becomes lower than the second threshold value while the first timer operates, the first timer is suspended. If the signal quality of the serving beam is lower than the first threshold value, and the collective signal quality of the specific beam group is lower than the second threshold value, the PHY reports a “radio link problem” indicator to the upper layer. The “radio link problem” indicator corresponds to the “out-of-sync” indicator in the LTE. If the upper layer firstly receives the “radio link problem” indicator as a report, a second timer operates, and if the second timer expires, the terminal declares the RLF. The terminal that has declared the RLF performs a second process. The second process means a process of reporting the RLF to the network after establishing a connection to a reestablishment process. If the signal quality of the serving beam becomes better than the first threshold value, or the signal quality of the specific beam group becomes better than the second threshold value while the second timer operates, the second timer is suspended. The first threshold value and the second threshold value may be determined through terminal implementation, or may be configured by the network. The first timer and the second timer may use fixed values or may be configured by the network.

FIG. 4H is a diagram explaining the operation of a terminal in RLM/RLF according to an embodiment of the present disclosure.

Referring to FIG. 4H, at operation 4 h-05, a terminal derives a first threshold value and a second threshold value. As an example of a derivation method, the first threshold value is a signal quality value that satisfies a specific BLER of a PDCCH of a serving beam. Since the relationship between the first threshold value and the BLER is influenced by the terminal performance, it is derived through terminal implementation. The second threshold value is a signal quality value that satisfies a specific BLER of a PDCCH of a specific beam. Since the relationship between the second threshold value and the BLER is influenced by the terminal performance, it is derived through terminal implementation. Further, the first threshold value and the second threshold value may be provided from a network. At operation 4 h-10, the terminal receives beam group configuration information provided from the network. The configuration information is used to configure a beam group. The information is provided to the terminal through system information being broadcast or dedicated RRC signaling. At operation 4 h-15, the terminal configures one group composed of specific beams in a TRP which the serving belongs to. At operation 4 h-20, the terminal measures the signal qualities of the downlink serving beam and the beam group for a specific period. At operation 4 h-25, the terminal determines whether the signal quality of the serving beam is better than the first threshold value. If the signal quality of the serving beam is better than the first threshold value, the terminal, at operation 4 h-30, maintains data transmission/reception through the serving beam. Otherwise, at operation 4 h-35, the terminal also determines whether the collective signal quality of the beam group is better than the second threshold value. If the signal quality of the serving beam is lower than the first threshold value, and the collective signal quality of the specific beam group is higher than the second threshold value for a specific time, the terminal proceeds to operation 4 h-40. If the signal quality of the serving beam is lower than the first threshold value, and the collective signal quality of the specific beam group is lower than the second threshold value for a specific time, the terminal proceeds to operation 4 h-45. At operation 4 h-40, the terminal performs a first process. The first process is a process in which the serving beam is changed in the same TRP (radio link recovery). At operation 4 h-45, the terminal declares the RLF. At operation 4 h-50, the terminal performs a second process. In the second process, the terminal performs a reestablishment process, and after the connection establishment, the terminal reports the RLF to the network.

FIG. 4I is a diagram explaining a first process according to an embodiment of the present disclosure.

Referring to FIG. 4I, at operation 4 i-05, a terminal performs a random access process to the same TRP. The terminal transmits a preamble to all beams or a specific beam in the TRP. The terminal receives a random access response (RAR) from a specific beam in response to the preamble, and considers the beam that has transmitted the RAR as a beam having the best signal quality in the TRP or a beam that provides the specific signal quality. The RAR includes UL grant. At operation 4 i-10, the terminal transmits a MAC CE or RRC message indicating that the reason to perform the random access is link recovery using the UL grant. The link recovery means to change the serving beam to another beam in the same TRP. At operation 4 i-15, the terminal transmits the MAC CE or RRC message including signal quality information of each beam in the TRP, collective signal quality information of a beam group, or signal quality information of each beam in the group using the UL grant.

A base station that has received this will use this message to configure the serving beam for the terminal. At operation 4 i-20, the terminal receives serving beam configuration information. At operation 4 i-25, the terminal configures a new serving beam using the configuration information. As another option, the terminal may implicitly consider a specific beam that provides the RAR as a new serving beam.

FIG. 4J is a diagram explaining a second process according to an embodiment of the present disclosure.

Referring to FIG. 4J, the terminal measures all beams or a specific beam provided from the same TRP or an adjacent TRP in the reestablishment process, at operation 4 j-05, and searches for a TRP/beam providing the best signal quality or a TRP/beam providing a specific signal quality. At operation 4 j-10, the terminal performs a random access process. The terminal transmits a preamble to all beams or a specific beam in the same or an adjacent TRP. The terminal receives a RAR from a specific beam in response to the preamble, and considers the beam that has transmitted the RAR as a beam having the best signal quality in the TRP or a beam that provides the specific signal quality. At operation 4 j-15, the terminal connects to a new serving cell or beam. At operation 4 j-20, the terminal transmits a MAC CE or RRC message indicating that the reason to perform the random access is RLF. A common control channel (CCCH) is a kind of the RRC message.

FIG. 4K is a diagram illustrating the configuration of a terminal according to an embodiment of the present disclosure.

Referring to FIG. 4K, the terminal includes an RF processor 4 k-10, a baseband processor 4 k-20, a storage unit 4 k-30, and a controller 4 k-40.

The RF processor 4 k-10 performs a function for transmitting and receiving a signal through a radio channel, such as signal band conversion and amplification. That is, the RF processor 4 k-10 performs up-conversion of a baseband signal provided from the baseband processor 4 k-20 into an RF-band signal to transmit the converted signal to an antenna, and performs down-conversion of the RF-band signal received through the antenna into a baseband signal. For example, the RF processor 4 k-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC. Although only one antenna is illustrated in the drawing, the terminal may be provided with a plurality of antennas. Further, the RF processor 4 k-10 may include a plurality of RF chains. Further, the RF processor 4 k-10 may perform beamforming. For the beamforming, the RF processor 4 l-10 may adjust phases and sizes of signals transmitted or received through the plurality of antennas or antenna elements. Further, the RF processor may perform MIMO, and may receive several layers during performing of a MIMO operation.

The baseband processor 4 k-20 performs conversion between a baseband signal and a bit string in accordance with the PHY standard of the system. For example, during data transmission, the baseband processor 4 k-20 generates complex symbols by encoding and modulating a transmitted bit string. Further, during data reception, the baseband processor 4 k-20 restores a received bit string by demodulating and decoding the baseband signal provided from the RF processor 4 k-10. For example, in the case of following an OFDM method, during data transmission, the baseband processor 4 k-20 generates complex symbols by encoding and modulating a transmitted bit string, performs mapping of the complex symbols on subcarriers, and then configures OFDM symbols through the IFFT operation and CP insertion. Further, during data reception, the baseband processor 4 k-20 divides the baseband signal provided from the RF processor 4 k-10 in the unit of OFDM symbols, restores the signals mapped on the subcarriers through the FFT operation, and then restores the received bit string through demodulation and decoding.

The baseband processor 4 k-20 and the RF processor 4 k-10 transmit and receive the signals as described above. Accordingly, the baseband processor 4 k-20 and the RF processor 4 k-10 may be called a transmitter, a receiver, a transceiver, or a communication unit. Further, in order to support different radio connection technologies, at least one of the baseband processor 4 k-20 and the RF processor 4 k-10 may include a plurality of communication modules. Further, in order to process signals of different frequency bands, at least one of the baseband processor 4 k-20 and the RF processor 4 k-10 may include different communication modules. For example, the different radio connection technologies may include an LTE network and an NR network. Further, the different frequency bands may include SHF (e.g., 2·NR Hz or NR Hz) band and millimeter wave (mm Wave) (e.g., 60 GHz) band.

The storage unit 4 k-30 stores therein a basic program for an operation of the terminal, application programs, and data of configuration information. In particular, the storage unit 4 k-30 may store information related to a second connection node that performs wireless communication using the second radio connection technology. Further, the storage unit 4 k-30 provides stored data in accordance with a request from the controller 4 k-40.

The controller 4 k-40 controls the whole operation of the terminal. For example, the controller 4 k-40 transmits and receives signals through the baseband processor 4 k-20 and the RF processor 4 k-10. Further, the controller 4 k-40 records or reads data in or from the storage unit 4 k-30. For this, the controller 4 k-40 may include at least one processor. For example, the controller 4 k-40 may include a CP performing a control for communication and an AP controlling an upper layer, such as an application program. The controller 4 k-40 may include a multi-connection processor 4 k-42.

FIG. 4L is a diagram illustrating the configuration of a base station in a wireless communication system according to an embodiment of the present disclosure.

Referring to FIG. 4L, the base station includes an RF processor 4 l-10, a baseband processor 4 l-20, a backhaul communication unit 4 l-30, a storage unit 4 l-40, and a controller 4 l-50.

The RF processor 4 l-10 performs a function for transmitting and receiving a signal through a radio channel, such as signal band conversion and amplification. That is, the RF processor 4 l-10 performs up-conversion of a baseband signal provided from the baseband processor 4 l-20 into an RF-band signal to transmit the converted signal to an antenna, and performs down-conversion of the RF-band signal received through the antenna into a baseband signal. For example, the RF processor 4 l-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC. Although only one antenna is illustrated in the drawing, the first connection node may be provided with a plurality of antennas. Further, the RF processor 4 l-10 may include a plurality of RF chains. Further, the RF processor 4 l-10 may perform beamforming. For the beamforming, the RF processor 4 l-10 may adjust phases and sizes of signals transmitted or received through the plurality of antennas or antenna elements. Further, the RF processor may perform down MIMO operation through transmission of one or more layers.

The baseband processor 4 l-20 performs conversion between a baseband signal and a bit string in accordance with the PHY standard of the first radio connection technology. For example, during data transmission, the baseband processor 4 l-20 generates complex symbols by encoding and modulating a transmitted bit string. Further, during data reception, the baseband processor 4 l-20 restores a received bit string by demodulating and decoding the baseband signal provided from the RF processor 4 l-10. For example, in the case of following an OFDM method, during data transmission, the baseband processor 4 l-20 generates complex symbols by encoding and modulating a transmitted bit string, performs mapping of the complex symbols on subcarriers, and then configures OFDM symbols through the IFFT operation and CP insertion. Further, during data reception, the baseband processor 4 l-20 divides the baseband signal provided from the RF processor 4 l-20 in the unit of OFDM symbols, restores the signals mapped on the subcarriers through the FFT operation, and then restores the received bit string through demodulation and decoding. The baseband processor 4 l-20 and the RF processor 4 l-10 transmit and receive the signals as described above. Accordingly, the baseband processor 4 l-20 and the RF processor 4 l-10 may be called a transmitter, a receiver, a transceiver, or a communication unit.

The backhaul communication unit 4 l-30 provides an interface for performing communication with other nodes in the network. That is, the backhaul communication unit 4 l-30 converts a bit string that is transmitted from the master base station to another node, for example, an auxiliary base station or a CN, into a physical signal, and converts a physical signal that is received from the other node into a bit string.

The storage unit 4 l-40 stores therein a basic program for an operation of the master base station, application programs, and data of configuration information. In particular, the storage unit 4 l-40 may store information on a bearer allocated to the connected terminal and the measurement result reported from the connected terminal. Further, the storage unit 4 l-40 may store information that becomes a basis of determination whether to provide or suspend a multi-connection to the terminal. Further, the storage unit 4 l-40 provides stored data in accordance with a request from the controller 4 l-50.

The controller 4 l-50 controls the whole operation of the master base station. For example, the controller 4 l-50 transmits and receives signals through the baseband processor 4 l-20 and the RF processor 4 l-10 or through the backhaul communication unit 4 l-30. Further, the controller 4 l-50 records or reads data in or from the storage unit 4 l-40. For this, the controller 4 l-50 may include at least one processor. The controller 4 l-50 may include a multi-connection processor 4 l-52.

Fifth Embodiment

In a wireless mobile communication system, it may be necessary to suspend the use of a radio link between a terminal and a network. If data transmission/reception is performed through the radio link of which the use is suspended, a malfunction may occur between the terminal and the network. For example, a serial number that is used for data transmission/reception may be erroneously updated to cause a normal operation not to be performed hereafter, or uplink transmission may be performed in an extremely inferior situation to cause the occurrence of unnecessary interference.

In order to prevent such a problem, if a specific event occurs to suspend the use of the radio link, the terminal suspends not only the operation of a physical channel but also the use of a signaling radio bearer (SRB) and a data radio bearer (DRB). In this case, through sensing of the kind of the event occurring, the terminal suspends the use of all SRBs or partial SRBs.

The event may be, for example, a start of a RLF or RRC connection suspension procedure.

If the RLF is sensed, the terminal starts a cell selection process to search for a cell in which a radio connection can be resumed, and starts an RRC connection reestablishment procedure in the newly selected cell. The RRC connection reestablishment procedure is a process in which the terminal transmits a specific RRC control message to a base station, and the base station transmits another specific control message to the terminal in response to the RRC control message. In this case, the uplink RRC control message and the downlink RRC control message are transmitted and received through a bearer that is called SRB0. The SRB0 is a radio bearer of which the security is not supported, and thus integrity is not secured with respect to the downlink control message transmitted through the SRB0.

The RRC connection suspension procedure may start as the base station transmits a specific control message to the terminal. The RRC connection suspension procedure is a procedure in which the terminal and the base station store therein currently used configuration information (it may be called context, and includes, for example, radio bearer configuration information, security key information, and radio measurement configuration information), and during the next RRC connection, the RRC connection is resumed more quickly using the stored configuration information. Since the terminal and the base station already share the security configuration information, integrity protection is applied with respect to the first downlink control message, and for this, the first downlink control message is transmitted using SRB1.

In the case where an event occurs to suspend the radio bearer, and the event is the RLF, the terminal suspends the operations of all SRBs excluding the SRB0, whereas if the event is caused by the RRC connection suspension procedure, the terminal suspends the operations of all SRBs excluding the SRB0 and SRB1, so that the following communication suspension procedure can be properly performed.

FIG. 5A is a diagram illustrating the structure of an LTE system to which partial embodiments of the present disclosure are applied according to an embodiment of the present disclosure.

Referring to FIG. 5A, a radio access network of an LTE system includes ENBs, “node Bs”, or “base stations” 5 a-05, 5 a-10, 5 a-15, and 5 a-20, an MME 5 a-25, and an S-GW 5 a-30. UE or “terminal” 5 a-35 connects to an external network through the ENBs 5 a-05, 5 a-10, 5 a-15, and 5 a-20 and the S-GW 5 a-30. In FIG. 5A, the ENBs 5 a-05, 5 a-10, 5 a-15, and 5 a-20 correspond to existing node Bs of a universal mobile telecommunications system (UMTS). The ENB is connected to the UE 5 a-35 through a radio channel, and plays a role that is more complicate than the role of the existing node B. In the LTE system, since all user traffics including real-time services, such as a voice over Internet protocol (VoIP), through the Internet protocol are serviced through shared channels, devices that perform scheduling through consolidation of status information, such as a buffer state, an available transmission power state, and a channel state, of UEs, and the ENBs 5 a-05, 5 a-10, 5 a-15, and 5 a-20 take charge of this. In general, one ENB controls a plurality of cells. In order to implement a transmission speed of several hundred Mbps, the LTE system uses OFDM as a radio connection technology in a 20 MHz bandwidth. Further, an AMC method that determines a modulation scheme and a channel coding rate to match the channel state of the terminal is applied. The S-GW 5 a-30 is a device that provides data bearers, and generates or removes the data bearers under the control of the MME 5 a-25. The MME is a device that takes charge of not only a mobility management function for the terminal but also various kinds of control functions, and is connected to a plurality of base stations.

FIG. 5B is a diagram illustrating a radio protocol structure of an LTE system to which an embodiment of the present disclosure is applied.

Referring to FIG. 5B, in a terminal or an ENB, a radio protocol of an LTE system is composed of a PDCP 5 b-05 or 5 b-40, an RLC 5 b-10 or 5 b-35, and an MAC 5 b-15 or 5 b-30. The PDCP 5 b-05 or 5 b-40 takes charge of IP header compression/decompression operations, ciphering/deciphering, and integrity security, and performs an ARQ operation through reconfiguration of a PDCP PDU with a proper size. The MAC 5 b-15 or 5 b-30 is connected to various RLC layer devices configured in one terminal, and performs multiplexing of RLC PDUs/MAC SDUs to a MAC PDU and demultiplexing of the RLC PDUs from the MAC PDU. A PHY 5 b-20 or 5 b-25 performs channel coding and modulation of upper layer data and produces OFDM symbols to transmit the OFDM symbols through a radio channel, or performs demodulation and channel decoding of the OFDM symbols received through the radio channel to transfer the demodulated and decoded OFDM symbols to an upper layer.

A radio bearer is a logical path formed to provide a proper QoS, and is composed of one PDCP device and one or two RLC devices. The radio bearer that processes data generated on an upper layer, for example, an IP layer, of a user plane is called a DRB. A radio bearer connected to an RRC to process data generated on the RRC is called an SRB. Maximally 3 SRBs may be configured in one terminal.

SRB0: This is a radio bearer that processes a CCCH control message, and security is not applied thereto. Only packets of a specific size are transmitted to an upper link. A PDCP header and an RLC header are not added to an RRC control message transmitted/received to/from the SRB0. In other words, the RRC control message is directly transferred to the MAC without separately processed through the PDCP and the RLC. Further, a message authentication code for integrity (MAC-I) for integrity protection is not added to a downlink RRC control message that is transmitted/received to/from the SRB0.

SRB1: This is a radio bearer that processes a dedicate control channel (DCCH) control message. The MAC-I is attached to data that is transmitted/received through the SRB1, and a PDCP layer is added to the MAC-I.

SRB2: This is a radio bearer that processes a dedicated control channel (DCCH) control message. Through the SRB2, a control message having a low priority, as compared with the control message that is transmitted/received through the SRB1, is transmitted/received.

The SRB0 is usable without any separate configuration procedure, whereas the SRB1 is configured in an RRC connection establishment process, and the SRB2 is configured in an RRC connection reconfiguration process.

FIG. 5C is a diagram explaining the operations of an RLF-related terminal and a network according to an embodiment of the present disclosure.

Referring to FIG. 5C, in a mobile communication system composed of a terminal 5 c-05 and a base station 5 c-10, the terminal 5 c-05 recognizes occurrence of an RLF, at operation 5 c-15. A case where the RLF has occurred means a case where a situation that a normal communication is unable to be performed between the terminal 5 c-05 and the base station 5 c-10 has occurred. For example, a situation that the quality of a downlink channel of a serving cell is currently lower than a specific reference is maintained over a predetermined time may occur. The terminal 5 c-05 that has recognized the occurrence of the RLF suspends the remaining SRBs and DRBs excluding the SRB0, at operation 5 c-20.

The terminal 5 c-05 starts a cell selection process to search for a cell in which the downlink channel quality that is higher than the specific reference is provided, at operation 5 c-25, and starts a random access process in one of the searched cells.

If an uplink transmission resource is allocated through the random access process, the terminal 5 c-05 transmits an RRC connection reestablishment request (RRCConnectionReestablishmentRequest) message through the SRB0 using the allocated uplink transmission resource, at operation 5 c-30. The control message includes terminal identifier information, specific code information/security token information generated by a security key of the terminal, and connection reestablishment cause information.

The base station 5 c-10 has information related to an RRC connection of the terminal 5 c-05 that has transmitted the control message, and if the security token is correct, it accepts the connection reestablishment request, and transmits an RRC connection reestablishment message to the terminal through the SRB0, at operation 5 c-35. The control message may include information necessary for security activation, for example, information related to a security key, and the terminal that has received the control message generates the security key, activates integrity protection and ciphering/deciphering, and resumes the operation of the SRB1, at operation 5 c-40. The information related to the security key may be NextHopChainingCount (NCC) (see 36.331). Thereafter, the terminal performs an RRC connection reconfiguration process through applying of the resumed SRB1 and the activated security, at operation 5 c-45, and the SRB2 and DRBs resume their operations through that above-described process.

FIG. 5D is a diagram explaining the operations of a terminal and a network that are related to an RRC connection suspension/release according to an embodiment of the present disclosure.

Referring to FIG. 5D, in a mobile communication system composed of a terminal 5 d-05 and a base station 5 d-10, the base station 5 d-10 determines to suspend an RRC connection of the terminal 5 d-05, and transmits an RRC control message including specific control information to the terminal 5 d-05, at operation 5 d-15. For example, if it is expected to resume communication with the terminal 5 d-05 in time although there exists no data to be transmitted to or received from the terminal 5 d-05, the base station 5 d-10 may suspend the RRC connection rather than releasing the RRC connection of the terminal 5 d-05. The specific information may be, for example, a resume identity to be used when the terminal 5 d-05 resumes the RRC connection and paging region information. The paging region information may be, for example, a list of cells, and the terminal 5 d-05 may reselect a cell that belongs to the paging region without any separate notification. In the case of reselecting a cell that does not belong to the paging region, the terminal 5 d-05 in the new cell notifies the base station 5 d-10 that the terminal has moved to the new paging region through transmission of an RRC control message to the base station 5 d-10.

The terminal 5 d-05 that has received the RRC control message including the specific control information suspends all SRBs and DRBs excluding the SRB0 and SRB1, at operation 5 d-20, and performs an operation of determining whether to stay in the current cell or to move to a new cell, that is, a cell reselection operation, in consideration of the downlink channel quality of the current serving cell and the downlink channel quality of a neighbor cell.

Thereafter, if new uplink data is generated in the terminal 5 d-05 at a certain time, the terminal starts a random access process in the current serving cell to resume the RRC connection. During the random access process, the terminal 5 d-05 is allocated with an uplink transmission resource from the terminal 5 d-05, and transmits a specific RRC control message, at operation 5 d-25. The RRC control message is a control message for requesting RRC connection resumption, and includes the resume identity information allocated at operation 5 d-15. The control message is transmitted through the uplink SRB0.

The base station 5 d-10 that has received the control message identifies a base station storing the context of the terminal 5 d-05 through checking of the control identity, and then receives the context of the terminal 5 d-05 from the base station 5 d-10. Further, the base station 5 d-10 recognizes SRB1 configuration of the terminal 5 d-05, SRB2 configuration, a security key currently used by the terminal 5 d-05, and DRB configuration using the received context, and transmits a control message for instructing the terminal 5 d-05 to resume the RRC connection through applying of the existing configuration of the terminal 5 d-05, at operation 5 d-30. The control message is transmitted through the SRB1, and the PDCP generates a MAC-I using the current security key, and transmits the MAC-I in a state where the MAC-I is appended at the back of the RRC control message.

The terminal 5 d-05 that has received the control message performs integrity verification through checking of the MAC-I, and resumes the RRC connection using the information in the control message, at operation 5 d-35. More specifically, the terminal 5 d-05 resumes the operations of the SRB2 and DRBs, calculates a new security key by applying the security information included in the control message, for example, NCC, and then uses the new security key during data transmission/reception. In order to apply the new security key, the terminal 5 d-05 reestablishes RLC devices and PDCP devices of the SRB1 of which the operation has already been resumed and the SRB2 of which the operation is resumed. The reestablishment of the RLC device means initialization of an RLC serial number and various kinds of variables, and the reestablishment of the PDCP device means initialization of a PDCP serial number and HFN to “0.”

FIG. 5E is a diagram explaining the operation of a terminal according to an embodiment of the present disclosure.

Referring to FIG. 5E, at operation 5 e-05, the terminal senses that an event in which at least one DRB should be suspended has occurred. Further, the terminal senses an event that makes the current RRC connection not used any more has occurred.

At operation 5 e-10, the terminal checks the kind of the event, and if the event is caused by a RLF, it proceeds to operation 5 e-15, whereas if the event is caused by reception of a specific RRC control message, it proceeds to operation 5 e-30. The specific RRC control message may be a control message including resume identity and paging region information.

At operation 5 e-15, the terminal suspends the remaining SRBs excluding the SRB0, that is, the SRB1 and SRB2, and performs a cell selection process until an RRC connection resumption condition is triggered. At operation 5 e-20, if the RRC connection resumption condition is triggered, for example, if a cell in which RRC connection reestablishment can be attempted is searched for, the terminal transmits a specific RRC control message (RRC connection reestablishment request message) through the SRB0. The RRC control message includes a terminal identifier and terminal security token information.

At operation 5 e-25, the terminal receives the specific RRC control message (RRC connection reestablishment message) through the SRB0. The terminal generates a new security key by applying an NCC included in the control message, and reestablishes the PDCP and RLC of the SRB1, at operation 5 e-27. Further, the terminal resumes the RRC connection operation in the cell.

At operation 5 e-30, the terminal receives the specific RRC control message, and suspends SRBs excluding the SRB0 and SRB1, that is, SRB2. The terminal inactivates integrity protection and ciphering/deciphering to process the downlink control message without checking the integrity through the SRB1 hereafter. The RRC control message includes information on resume identity or the like. Thereafter, the terminal performs a cell reselection process until the RRC connection resumption condition is triggered.

At operation 5 e-35, if the RRC connection resumption condition is triggered, for example, if uplink data is generated or a paging message is received, the terminal transmits a specific RRC control message (RRC connection resumption request message) through the SRB0. The control message includes the resume identity of the terminal. The resume identity of the RRC connection resumption request message and the terminal identifier of the RRC connection reestablishment request message are different from each other. The resume identity is a combination of the terminal identifier and the identifier of the old base station, whereas the terminal identifier is a terminal identifier used by the terminal with respect to the old base station, and does not include information related to the base station.

At operation 5 e-40, the terminal receives the specific RRC control message and the MAC-I for the RRC control message through the SRB1. The terminal generates a new security key using the NCC included in the RRC control message, activates integrity protection, and then verifies the MAC-I through applying of the new security key, at operation 5 e-45. If the integrity verification is successful, the terminal performs an operation indicated by the RRC control message, for example, resumption of the operations of the SRB2 and DRBs and ciphering/deciphering activation. In this case, the terminal initializes the serial number of the protocol, count, and various kinds of variables through reestablishment of the PDCP and RLC of the SRB1.

FIG. 5F is a diagram illustrating the configuration of a terminal according to an embodiment of the present disclosure.

Referring to FIG. 5F, the terminal includes an RF processor 5 f-10, a baseband processor 5 f-20, a storage unit 5 f-30, and a controller 5 f-40.

The RF processor 5 f-10 performs a function for transmitting and receiving a signal through a radio channel, such as signal band conversion and amplification. That is, the RF processor 5 f-10 performs up-conversion of a baseband signal provided from the baseband processor 5 f-20 into an RF-band signal to transmit the converted signal to an antenna, and performs down-conversion of the RF-band signal received through the antenna into a baseband signal. For example, the RF processor 5 f-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC. Although only one antenna is illustrated in the drawing, the terminal may be provided with a plurality of antennas. Further, the RF processor 5 f-10 may include a plurality of RF chains.

The baseband processor 5 f-20 performs conversion between a baseband signal and a bit string in accordance with the PHY standard of the system. For example, during data transmission, the baseband processor 5 f-20 generates complex symbols by encoding and modulating a transmitted bit string. Further, during data reception, the baseband processor 5 f-20 restores a received bit string by demodulating and decoding the baseband signal provided from the RF processor 5 f-10. For example, in the case of following an OFDM method, during data transmission, the baseband processor 5 f-20 generates complex symbols by encoding and modulating a transmitted bit string, performs mapping of the complex symbols on subcarriers, and then configures OFDM symbols through the IFFT operation and CP insertion. Further, during data reception, the baseband processor 5 f-20 divides the baseband signal provided from the RF processor 5 f-10 in the unit of OFDM symbols, restores the signals mapped on the subcarriers through the FFT operation, and then restores the received bit string through demodulation and decoding.

The baseband processor 5 f-20 and the RF processor 5 f-10 transmit and receive the signals as described above. Accordingly, the baseband processor 5 f-20 and the RF processor 5 f-10 may be called a transmitter, a receiver, a transceiver, or a communication unit. Further, in order to support different radio connection technologies, at least one of the baseband processor 5 f-20 and the RF processor 5 f-10 may include a plurality of communication modules. Further, in order to process signals of different frequency bands, at least one of the baseband processor 5 f-20 and the RF processor 5 f-10 may include different communication modules.

The storage unit 5 f-30 stores therein a basic program for an operation of the terminal, application programs, and data of configuration information. The storage unit 5 f-30 provides stored data in accordance with a request from the controller 5 f-40.

The controller 5 f-40 controls the whole operation of the terminal. For example, the controller 5 f-40 transmits and receives signals through the baseband processor 5 f-20 and the RF processor 5 f-10. Further, the controller 5 f-40 records or reads data in or from the storage unit 5 f-30. Further, the controller 5 f-40 controls suspension and operation resumption of the SRB and DRB. For this, the controller 5 f-40 may include at least one processor. For example, the controller 5 f-40 may include a CP performing a control for communication and an AP controlling an upper layer, such as an application program. The controller 5 f-40 may include a multi-connection processor 5 f-42.

FIG. 5G is a diagram illustrating the configuration of a base station in a wireless communication system according to an embodiment of the present disclosure.

Referring to FIG. 5G, the base station includes an RF processor 5 g-10, a baseband processor 5 g-20, a backhaul communication unit 5 g-30, a storage unit 5 g-40, and a controller 5 g-50.

The RF processor 5 g-10 performs a function for transmitting and receiving a signal through a radio channel, such as signal band conversion and amplification. That is, the RF processor 5 g-10 performs up-conversion of a baseband signal provided from the baseband processor 5 g-20 into an RF-band signal to transmit the converted signal to an antenna, and performs down-conversion of the RF-band signal received through the antenna into a baseband signal. For example, the RF processor 5 g-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC. Although only one antenna is illustrated in the drawing, the first connection node may be provided with a plurality of antennas. Further, the RF processor 5 g-10 may include a plurality of RF chains.

The baseband processor 5 g-20 performs conversion between a baseband signal and a bit string in accordance with the PHY standard of the first radio connection technology. For example, during data transmission, the baseband processor 5 g-20 generates complex symbols by encoding and modulating a transmitted bit string. Further, during data reception, the baseband processor 5 g-20 restores a received bit string by demodulating and decoding the baseband signal provided from the RF processor 5 g-10. For example, in the case of following an OFDM method, during data transmission, the baseband processor 5 g-20 generates complex symbols by encoding and modulating a transmitted bit string, performs mapping of the complex symbols on subcarriers, and then configures OFDM symbols through the IFFT operation and CP insertion. Further, during data reception, the baseband processor 5 g-20 divides the baseband signal provided from the RF processor 5 g-10 in the unit of OFDM symbols, restores the signals mapped on the subcarriers through the FFT operation, and then restores the received bit string through demodulation and decoding. The baseband processor 5 g-20 and the RF processor 5 g-10 transmit and receive the signals as described above. Accordingly, the baseband processor 5 g-20 and the RF processor 5 g-10 may be called a transmitter, a receiver, a transceiver, or a communication unit.

The backhaul communication unit 5 g-30 provides an interface for performing communication with other nodes in the network.

The storage unit 5 g-40 stores therein a basic program for an operation of the master base station, application programs, and data of configuration information. In particular, the storage unit 5 g-40 may store information on a bearer allocated to the connected terminal and the measurement result reported from the connected terminal. Further, the storage unit 5 g-40 may store information that becomes a basis of determination whether to provide or suspend a multi-connection to the terminal. Further, the storage unit 5 g-40 provides stored data in accordance with a request from the controller 5 g-50.

The controller 5 g-50 controls the whole operation of the master base station. For example, the controller 5 g-50 transmits and receives signals through the baseband processor 5 g-20 and the RF processor 5 g-10 or through the backhaul communication unit 5 g-30. Further, the controller 5 g-50 records or reads data in or from the storage unit 5 g-40. For this, the controller 5 g-50 may include at least one processor. The controller 5 g-50 may include a multi-connection processor 5 g-52.

Sixth Embodiment

In a wireless mobile communication system, it may be necessary to suspend the use of a radio link between a terminal and a network. If data transmission/reception is performed through the radio link of which the use is suspended, a malfunction may occur between the terminal and the network. For example, a serial number that is used for data transmission/reception may be erroneously updated to cause a normal operation not to be performed hereafter, or uplink transmission may be performed in an extremely inferior situation to cause the occurrence of unnecessary interference.

In order to prevent such a problem, if a specific event occurs to suspend the use of the radio link, the terminal suspends not only the operation of a physical channel but also the use of a SRB.

The RRC connection suspension procedure may start as the base station transmits a specific control message to the terminal. The RRC connection suspension procedure is a procedure in which the terminal and the base station store therein currently used configuration information (it may be called UE context, and includes, for example, radio bearer configuration information, security key information, and radio measurement configuration information. Hereinafter referred to as “terminal context”), and during the next RRC connection, the RRC connection is resumed more quickly using the stored configuration information. Since the terminal and the base station already share the security configuration information, integrity protection is applied with respect to the first downlink control message, and for this, the first downlink control message is transmitted using SRB1.

However, if the base station to which the terminal intends to resume connection is not the base station previously connected to the terminal, but a new base station due to mobility of the terminal, a problem may occur in receiving the first downlink control message. This is because if the new base station has security configuration that is different from the security configuration of the terminal, the terminal is unable to decode the encrypted control message that the terminal has received from SRB1. This problem may occur because NextHopChainingCount (hereinafter referred to as “NCC”) values that the base station allocates to the terminal may be basically different from each other by base stations.

An embodiment of the present disclosure proposes the operations of the base station and the terminal so that the base station and the terminal can normally transmit/receive the control message to/from each other even if the terminal is connected to a new base station in the case where the base station and the terminal resume their connection after suspending the same.

The (6-1)-th embodiment of the present disclosure proposes a method in which an NCC to be used during the next connection resumption is pre-allocated to an RRC connection release message that is transmitted by a base station to suspend a connection to a terminal, and when the connection is resumed, the terminal reestablishes a PDCP of SRB1 through generation of a new security key using the NCC, so that the terminal and the base station can normally transmit and receive a control message.

For a specific reason, the base station may release the connection to the terminal. When releasing the connection to the terminal, the base station transmits an RRC connection release message (first RRC message) to the terminal. The first RRC message may include a resume identity to be used by the terminal when resuming the RRC connection, a NextHopChainingCount (NCC), and paging region information. If the message is received, the terminal may be shifted to an RRC idle state or an RRC inactive state after storing the terminal context and the NCC to be used when resuming the connection hereafter. The terminal context is also called UE context, and includes, for example, radio bearer configuration information, security key information, and radio measurement configuration information. The terminal may move between cells without reporting such movement to the base station in the paging region, and if the terminal gets out of the paging region, it may report the current cell and update the paging region. The paging region may indicate a list of cells or a paging identification (ID). If the base station and the terminal intend to resume their connection for a specific reason, the terminal includes a resume identity (resume ID) in an RRC connection resumption request message (second RRC message) to transmit the same to the current cell. Before transmitting the RRC connection resumption request message, the terminal performs synchronization with the current cell to know a target physical cell identity (PCI) and a target frequency. Before transmitting the RRC connection resumption request message, the terminal receives generates a new security key using the target PCI and target frequency of the current cell, and the NCC that is received from the first RRC message to be stored, and reestablishes the PDCP of the SRB1 based on this. Further, the terminal transmits the RRC connection resumption request message, receives an RRC connection resumption message (third message) in response to this, and decodes and confirms the RRC connection resumption message with the established PDCP of the SRB1.

The (6-1)-th embodiment of the present disclosure includes the following operations.

-   -   An operation at which the terminal receives a first RRC message         including a resume identity (resume ID) and a NextHopChaining         Count (NCC).     -   An operation at which the terminal starts UE based mobility         after receiving the first RRC message.     -   An operation at which one of predefined events occurs.     -   An operation at which the received NCC and the terminal         generates a new security key based on a cell identity of the         current cell.     -   An operation at which the terminal reestablishes a PDCP of SRB1.     -   An operation at which the terminal transmits a second RRC         message including the resume identity (resume ID) to the current         cell.     -   An operation at which the terminal receives a third RRC message         from the current cell through SRB1.     -   An operation at which the terminal decodes and confirms the         received third RRC message with the generated new security key.     -   An operation at which the terminal resumes DRBs in accordance         with the third RRC message and transmits data through the DRBs.

The second RRC message is transmitted to SRB0, and the predefined events may include the followings.

-   -   A case where the terminal receives a paging message from the         current cell.     -   A case where the terminal receives downlink scheduling         information from the current cell.     -   A case where uplink data to be transmitted by the terminal         occurs.

The (6-2)-th embodiment of the present disclosure proposes a method in which a base station includes an NCC in unencrypted PDCP control PDU of an RRC connection resumption message to be transmitted if a connection is resumed after the base station suspends the connection to a terminal, and the terminal receives the NCC, generates a new security key based on this, and establishes a PDCP of SRB1, so that the terminal and the base station can normally transmit and receive a control message.

For a specific reason, the base station may release the connection to the terminal. When releasing the connection to the terminal, the base station transmits an RRC connection release message (first RRC message) to the terminal. The first RRC message may include a resume identity to be used by the terminal when resuming the RRC connection and paging region information. If the message is received, the terminal may be shifted to an RRC idle state or an RRC inactive state after storing the terminal context and the NCC to be used when resuming the connection hereafter. The terminal context is also called UE context, and may include, for example, radio bearer configuration information, security key information, and radio measurement configuration information. The terminal may move between cells without reporting such movement to the base station in the paging region, and if the terminal gets out of the paging region, it may report the current cell and update the paging region. The paging region may indicate a list of cells or a paging ID. If the base station and the terminal intend to resume their connection for a specific reason, the terminal includes a resume identity (resume ID) in an RRC connection resumption request message (second RRC message) to transmit the same to the current cell. Before transmitting the RRC connection resumption request message, the terminal performs synchronization with the current cell to know a target PCI and a target frequency. The base station receives the RRC connection resumption request message, analyzes the resume ID, and transmits a terminal context request message (first message) to the old base station of the terminal. In this case, the old base station generates a new security key based on the NCC, a target PCI of a new base station, and a target frequency, and transfers both the security key and the NCC to the new base station. The new base station transmits to the terminal the RRC connection resumption message (third RRC message) and the unencrypted PDCP control PDCU including the NCC in response to the RRC connection resumption request message of the terminal. The terminal receives the RRC connection resumption message, confirms the NCC in the unencrypted PDCP control PDU, generates a new security key together with the target PCI and the target frequency, establishes the PDCP of the SRB1, confirms the RRC connection resumption message, and performs a connection resumption procedure.

The (6-2)-th embodiment of the present disclosure includes the following operations.

-   -   An operation at which the terminal receives a first RRC message         including a resume identity (resume ID).     -   An operation at which the terminal starts UE based mobility         after receiving the first RRC message.     -   An operation at which one of predefined events occurs.     -   An operation at which the terminal transmits a second RRC         message including the resume identity (resume ID) to the current         cell.     -   An operation at which a new base station requests terminal         context from the old base station of the terminal.     -   An operation at which the old base station generates a new         security key using the NCC and information (PCI and frequency)         of a new base station (current cell of the terminal).     -   An operation at which the old base station transfers the new         security key and the NCC to the new base station.     -   An operation at which the new base station includes the NCC in         the unencrypted PDCP control PDU to be generated.     -   An operation at which the new base station transmits a third RRC         message and the PDCP control PDU including the NCC to SRB1.     -   An operation at which the terminal receives the third RRC         message from the current cell through SRB1.     -   An operation at which the terminal confirms the NCC from the         unencrypted PDCP control PDU.     -   An operation at which the received NCC and the terminal generate         a new security key based on a cell identity of the current cell.     -   An operation at which the terminal reestablishes the PDCP of         SRB1 based on the new security keys.     -   An operation at which the terminal decodes and confirms the         received third RRC message with the generated new security key.     -   An operation at which the terminal resumes DRBs in accordance         with the third RRC message and transmits data through the DRBs.

The second RRC message is transmitted to SRB0, and the predefined events may include the followings.

-   -   A case where the terminal receives a paging message from the         current cell.     -   A case where the terminal receives downlink scheduling         information from the current cell.     -   A case where uplink data to be transmitted by the terminal         occurs

FIG. 6A is a diagram illustrating the structure of an LTE system to which partial embodiments of the present disclosure are applied according to an embodiment of the present disclosure.

Referring to FIG. 6A, a radio access network of an LTE system includes ENBs, “node Bs”, or “base stations” 6 a-05, 6 a-10, 6 a-15, and 6 a-20, an MME 6 a-25, and an S-GW 6 a-30. UE or “terminal” 6 a-35 connects to an external network through the ENBs 6 a-05, 6 a-10, 6 a-15, and 6 a-20 and the S-GW 6 a-30. In FIG. 6A, the ENBs 6 a-05, 6 a-10, 6 a-15, and 6 a-20 correspond to existing node Bs of a UMTS. The ENB is connected to the UE 6 a-35 through a radio channel, and plays a role that is more complicate than the role of the existing node B. In the LTE system, since all user traffics including real-time services, such as VoIP, through the Internet protocol are serviced through shared channels, devices that perform scheduling through consolidation of status information, such as a buffer state, an available transmission power state, and a channel state, of UEs, and the ENBs 6 a-05, 6 a-10, 6 a-15, and 6 a-20 take charge of this. In general, one ENB controls a plurality of cells. In order to implement a transmission speed of several hundred Mbps, the LTE system uses OFDM as a radio connection technology in a 20 MHz bandwidth. Further, an AMC method that determines a modulation scheme and a channel coding rate to match the channel state of the terminal is applied. The S-GW 6 a-30 is a device that provides data bearers, and generates or removes the data bearers under the control of the MME 6 a-25. The MME is a device that takes charge of not only a mobility management function for the terminal but also various kinds of control functions, and is connected to a plurality of base stations.

FIG. 6B is a diagram illustrating a radio protocol structure of an LTE system to which an embodiment of the present disclosure is applied according to an embodiment of the present disclosure.

Referring to FIG. 6B, in a terminal or an ENB, a radio protocol of an LTE system is composed of a PDCP 6 b-05 or 6 b-40, an RLC 6 b-10 or 6 b-35, and an MAC 6 b-15 or 6 b-30. The PDCP 6 b-05 or 6 b-40 takes charge of IP header compression/decompression operations, ciphering/deciphering, and integrity security, and performs an ARQ operation through reconfiguration of a PDCP PDU with a proper size. The MAC 6 b-15 or 6 b-30 is connected to various RLC layer devices configured in one terminal, and performs multiplexing of RLC PDUs/MAC SDUs to a MAC PDU and demultiplexing of the RLC PDUs from the MAC PDU. A PHYs 6 b-20 or 6 b-25 performs channel coding and modulation of upper layer data and produces OFDM symbols to transmit the OFDM symbols through a radio channel, or performs demodulation and channel decoding of the OFDM symbols received through the radio channel to transfer the demodulated and decoded OFDM symbols to an upper layer.

A radio bearer is a logical path formed to provide a proper QoS, and is composed of one PDCP device and one or two RLC devices. The radio bearer that processes data generated on an upper layer, for example, an IP layer, of a user plane is called a DRB. A radio bearer connected to an RRC to process data generated on the RRC is called an SRB. Maximally 3 SRBs may be configured in one terminal.

SRB0: This is a radio bearer that processes a CCCH control message, and security is not applied thereto. Only packets of a specific size are transmitted to an upper link. A PDCP header and an RLC header are not added to an RRC control message transmitted/received to/from the SRB0. In other words, the RRC control message is directly transferred to the MAC without separately processed through the PDCP and the RLC. Further, a MAC-I for integrity protection is not added to a downlink RRC control message that is transmitted/received to/from the SRB0.

SRB1: This is a radio bearer that processes a DCCH control message. The MAC-I is attached to data that is transmitted/received through the SRB1, and a PDCP layer is added to the MAC-I.

SRB2: This is a radio bearer that processes a DCCH control message. Through the SRB2, a control message having a low priority, as compared with the control message that is transmitted/received through the SRB1, is transmitted/received.

The SRB0 is usable without any separate configuration procedure, whereas the SRB1 is configured in an RRC connection establishment process, and the SRB2 is configured in an RRC connection reconfiguration process.

FIGS. 6C and 6D are diagrams illustrating the (6-1)-th embodiment of the present disclosure.

FIG. 6C is a diagram explaining a procedure in which a network releases a connection to a terminal according to the (6-1)-th embodiment of the present disclosure.

Referring to FIG. 6C, in a mobile communication system composed of a terminal 6 c-01, a base station 6 c-02, an MME 6 c-03, and an S-GW 6 c-04, while the terminal 6 c-01 and a network transmit/receive data to/from each other, at operations 6 c-05 and 6 c-10, the base station 6 c-02 may determine to suspend an RRC connection of the terminal 6 c-01, at operation 6 c-15, and may release or suspend SRBs and DRBs, at operation 6 c-20. Further, the base station 6 c-02 transmits an RRC control message (RRC connection release message) including specific control information to the terminal 6 c-01, at operation 6 c-25. For example, if it is expected to resume communication with the terminal 6 c-01 in time although there exists no data to be transmitted to or received from the terminal 6 c-01, the base station 6 c-02 may suspend the RRC connection rather than releasing the RRC connection of the terminal 6 c-01. The specific information of the RRC connection release message may be, for example, a resume identity to be used when the terminal 6 c-01 resumes the RRC connection, NextHopChainingCount (NCC), and paging region information. The paging region information may be, for example, a list of cells, and the terminal 6 c-01 may reselect a cell that belongs to the paging region without notifying the base station 6 c-02 of any separate notification. In the case of reselecting a cell that does not belong to the paging region, the terminal 6 c-01 in the new cell may notify the base station 6 c-02 that the terminal has moved to the new paging region through transmission of an RRC control message to the base station 6 c-02, and may update the paging region. The terminal 6 c-01 that has received the RRC control message (RRC connection release message) including the specific control information suspends all SRBs and DRBs, at operation 6 c-30, and stores the terminal context and the NCC. The terminal context (that is also called a UE context) may include, for example, radio bearer configuration information, security key information, and radio measurement configuration information, and the NCC may be necessary for security configuration when further resuming the connection.

Then, the terminal performs an operation of determining whether to continuously stay in the current cell or to move to a new cell, i.e., cell reselection operation, in consideration of the downlink channel quality of the current serving cell and the downlink channel quality of a neighbor cell.

FIG. 6D is a diagram explaining a procedure in which the terminal and the network resume the connection according to the (6-1)-th embodiment of the present disclosure.

Referring to FIG. 6D, if a specific reason for resuming the connection occurs at a certain time, for example, if new uplink data occurs in the terminal 6 d-01, at operation 6 d-10, the terminal 6 d-01 starts a random access process in the current serving cell to resume the RRC connection, at operations 6 d-15 and 6 d-20. In the random access process, the terminal 6 d-01 is allocated with the uplink transmission resource for transmitting the specific RRC control message from the base station. The terminal generates new security keys using a target PCI, a target frequency, and the NCC received at operation 6 c-25 of FIG. 6C before sending the RRC control message. The security keys may include KeNB*. Further, a terminal 6 d-01 reestablishes a PDCP of SRB1 to apply the newly generated security keys, at operation 6 d-25.

If the operation of 6 d-25 is completed, the terminal 6 d-01 sends the RRC control message to a new base station 6 d-02, at operation 6 d-30. The RRC control message is a control message for requesting the RRC connection resumption, and may include information on resume identity (hereinafter referred to as resume ID) allocated at operation 6 c-25 of FIG. 6C, resumeCause, and shortResumeMAC-1. The control message is transmitted through an uplink SRB0.

The new base station 6 d-02 that has received the control message identifies an old base station 6 d-03 that stores the terminal context through checking of the resume ID, and then receives the terminal context from the old base station 6 d-03, at operations 6 d-35, 6 d-40, and 6 d-45. In this case, the old base station 6 d-03 generates new security keys using the NCC transferred when releasing the connection to the terminal 6 d-01 as shown in FIG. 6C, and PCI and frequency information of the currently new base station, and transfers the generated security keys to the new base station. The security keys may include KeNB*. Further, the new base station 6 d-02 transmits a control message for instructing the terminal to resume the RRC connection in order to resume the RRC connection through applying of terminal SRB1 configuration, SRB2 configuration, and DRB configuration using the received terminal contest and the new security keys, at operation 6 d-50.

The control message is transmitted through SRB1, and the PDCP generates a MAC-I using the current new security key, and transmits the MAC-I in a state where the MAC-I is appended at the back of the RRC control message. The control message may include the NCC. The terminal 6 d-01 that has received the control message performs integrity verification through checking of the MAC-I based on new security key generated at operation 6 d-25 and the PDCP of the established SRB1, and resumes the RRC connection using the information in the control message, at operation 6 d-55. More specifically, the terminal 6 d-01 resumes the operations of the SRB2 and DRBs, and reestablishes RLC devices and PDCP devices of the SRB2 and DRBs to apply the newly generated security keys. The reestablishment of the RLC device means initialization of an RLC serial number and various kinds of variables, and the reestablishment of the PDCP device means initialization of a PDCP serial number and HFN to “0”.

After completion of the above-described procedure, the terminal 6 d-01 sends a control message indicating that the resumption of the RRC connection has been completed to the new base station 6 d-02, at operation 6 d-60. The new base station 6 d-02 resumes the DRBs if it receives the RRC connection resumption completion message. If the DRBs are released, the new base station 6 d-02 performs a procedure of newly generating the DRBs, whereas if the DRBs are suspended, the base station performs procedures of correcting and resuming paths of the DRBs, at operation 6 d-65. Then, the new base station 6 d-02 requests the old base station 6 d-03 to release the terminal context, at operation 6 d-70. Thereafter, the terminal 6 d-01 transmits/receives data to/from the network in an RRC connection state, at operations 6 d-75 and 6 d-80.

FIG. 6E is a diagram explaining the operation of a terminal according to the (6-1)-th embodiment of the present disclosure.

Referring to FIG. 6E, if the base station determines to suspend an RRC connection of the terminal in a state where the terminal and the network transmit/receive data to/from each other, at operation 6 e-05, and transmits an RRC control message (RRC connection release message) including specific control information to the terminal, the terminal receives the RRC control message, at operation 6 e-10. The specific information of the RRC connection release message may be a resume identity to be used when the terminal resumes the RRC connection, NextHopChainingCount (NCC), and paging region information. The terminal that has received the RRC control message (RRC connection release message) including the control information suspends all SRBs and DRBs, and stores the terminal context and the NCC. The terminal context (that is also called a UE context) may include, for example, radio bearer configuration information, security key information, and radio measurement configuration information, and the NCC may be necessary for security configuration when further resuming the connection. Then, the terminal performs an operation of determining whether to continuously stay in the current cell or to move to a new cell, i.e., cell reselection operation, in consideration of the downlink channel quality of the current serving cell and the downlink channel quality of a neighbor cell. If a specific reason for resuming the connection occurs at a certain time, for example, if new uplink data occurs in the terminal, at operation 6 e-15, the terminal starts a random access process in the current serving cell to resume the RRC connection, at operation 6 e-20. In the random access process, the terminal is allocated with the uplink transmission resource for transmitting the specific RRC control message from the base station. The terminal generates new security keys using a target PCI, a target frequency, and the NCC received at operation 6 c-25 of FIG. 6C before sending the RRC control message. The security keys may include KeNB*. Further, the terminal reestablishes a PDCP and an RLC of SRB1 to apply the newly generated security keys, at operation 6 e-20.

If the operation of 6 e-20 is completed, the terminal sends the RRC control message to the base station, at operation 6 e-25. The RRC control message is a control message for requesting the RRC connection resumption, and may include information on resume identity (hereinafter referred to as resume ID) allocated at operation 6 e-10, resumeCause, and shortResumeMAC-1. The base station transmits a control message for instructing the terminal to resume the RRC connection in order to resume the RRC connection, and the terminal receives the control message, at operation 6 e-30. The control message is transmitted through SRB1, and in the base station, the PDCP generates a MAC-I using the current new security key, and transmits the MAC-I in a state where the MAC-I is appended at the back of the RRC control message. The control message may include the NCC. The terminal that has received the control message performs integrity verification through checking of the MAC-I based on new security key generated at operation 6 e-20 and the PDCP of the established SRB1, and resumes the RRC connection using the information in the control message, at operation 6 e-30. More specifically, the terminal resumes the operations of the SRB2 and DRBs, and reestablishes RLC devices and PDCP devices of the SRB2 and DRBs to apply the newly generated security keys. The reestablishment of the RLC device means initialization of an RLC serial number and various kinds of variables, and the reestablishment of the PDCP device means initialization of a PDCP serial number and HFN to “0”. After completion of the above-described procedure, the terminal sends a control message indicating that the resumption of the RRC connection has been completed to the base station, at operation 6 e-35.

FIGS. 6F and 6G are diagrams illustrating the (6-2)-th embodiment of the present disclosure.

FIG. 6F illustrates a procedure in which a network releases a connection to a terminal according to the (6-2)-th embodiment of the present disclosure.

Referring to FIG. 6F, in a mobile communication system composed of a terminal 6 f-01, a base station 6 f-02, an MME 6 f-03, and an S-GW 6 f-04, while the terminal 6 f-01 and a network transmit/receive data to/from each other, at operations 6 f-05 and 6 f-10, the base station 6 f-02 may determine to suspend an RRC connection of the terminal 6 f-01, at operation 6 f-15, and may release or suspend SRBs and DRBs, at operation 6 f-20. Further, the base station 6 f-02 transmits an RRC control message (RRC connection release message) including specific control information to the terminal 6 f-01, at operation 6 f-25. For example, if it is expected to resume communication with the terminal 6 f-01 in time although there exists no data to be transmitted to or received from the terminal 6 f-01, the base station 6 f-02 may suspend the RRC connection rather than releasing the RRC connection of the terminal 6 f-01. The specific information of the RRC connection release message may be, for example, a resume identity to be used when the terminal 6 f-01 resumes the RRC connection, NextHopChainingCount (NCC), and paging region information. The paging region information may be, for example, a list of cells, and the terminal 6 f-01 may reselect a cell that belongs to the paging region without notifying the base station 6 f-02 of any separate notification. In the case of reselecting a cell that does not belong to the paging region, the terminal 6 f-01 in the new cell may notify the base station 6 f-02 that the terminal 6 f-01 has moved to the new paging region through transmission of an RRC control message to the base station 6 f-02, and may update the paging region. The terminal 6 f-01 that has received the RRC control message (RRC connection release message) including the specific control information suspends all SRBs and DRBs, at operation 6 f-30, and stores the terminal context. The terminal context (that is also called a UE context) may include, for example, radio bearer configuration information, security key information, and radio measurement configuration information. The terminal 6 f-01 performs an operation of determining whether to continuously stay in the current cell or to move to a new cell, i.e., cell reselection operation, in consideration of the downlink channel quality of the current serving cell and the downlink channel quality of a neighbor cell.

FIG. 6G is a diagram illustrating a procedure in which the terminal and the network resume the connection according to the (6-2)-th embodiment of the present disclosure.

Referring to FIG. 6G, if a specific reason for resuming the connection occurs at a certain time, for example, if new uplink data occurs in a terminal 6 g-01, at operation 6 g-10, the terminal 6 g-01 starts a random access process in the current serving cell to resume the RRC connection, at operations 6 g-15 and 6 g-20. In the random access process, the terminal 6 g-01 is allocated with the uplink transmission resource for transmitting the specific RRC control message from a new base station 6 g-02, and sends the RRC control message to the new base station 6 g-02, at operation 6 g-25. The RRC control message is a control message for requesting the RRC connection resumption, and may include information on resume identity (hereinafter referred to as resume ID) allocated at operation 6 f-25 of FIG. 6F, resumeCause, and shortResumeMAC-1. The control message is transmitted through an uplink SRB0. The new base station 6 g-02 that has received the control message identifies the old base station 6 g-03 that stores the terminal context through checking of the resume ID, and then receives the terminal context from the base station, at operations 6 g-30 and 6 g-40. In this case, the old base station 6 g-03 may generate new security keys using a new NCC for new security configuration of the new base station 6 g-02, and PCI and frequency information of the currently new base station 6 g-02 of the terminal 6 g-01, and may transfer the new security keys to the new base station 6 g-02 together with the NCC. The security keys may include KeNB*. Operation 6 g-35 may be replaced by a procedure in which the old base station 6 g-03 sends the old security configuration keys KeNB* to the new base station 6 g-02, and the new base station 6 g-02 generates new security keys KeNB* using the NCC, PCI, and frequency information generated by the new base station. Further, the new base station may generate unencrypted PDCP control PUD to transfer the NCC information to the terminal 6 g-01 that does not know the new security configuration, at operation 6 g-45. The PDCP control PDU may include the NCC information. The new base station 6 g-02 transmits to the terminal 6 g-01 a control message for instructing the terminal 6 g-01 to resume the RRC connection in order to resume the RRC connection through applying of SRB1 configuration, SRB2 configuration, and DRB configuration using the terminal contest and the new security keys, and the unencrypted PDCP control PDU, at operation 6 g-50. The control message is transmitted through SRB1, and the PDCP generates a MAC-I using the current new security key, and transmits the MAC-I in a state where the MAC-I is appended at the back of the RRC control message. The control message may include the NCC. Since the terminal 6 g-01 that has received the control message is unable to decode the control message, it first receives the NCC from the unencrypted PDCP control PDU to transfer the NCC to an RRC layer, and the RRC layer generates new security keys using the NCC, target PCI and target frequency of the current cell, at operation 6 g-55. The security keys may include KeNB*. Further, in order to apply the new security keys, the PDCP and RLC of the SRB1 are reestablished, at operation 6 g-60. The terminal 6 g-01 performs integrity verification through checking of the MAC-I based on the new security key as generated above and the PDCP of the established SRB1, and resumes the RRC connection through confirming of the information included in the control message. More specifically, the terminal 6 g-01 resumes the operations of the SRB2 and DRBs, and reestablishes RLC devices and PDCP devices of the SRB2 and DRBs to apply the newly generated security keys. The reestablishment of the RLC device means initialization of an RLC serial number and various kinds of variables, and the reestablishment of the PDCP device means initialization of a PDCP serial number and HFN to “0”. After completion of the above-described procedure, the terminal 6 g-01 sends a control message indicating that the resumption of the RRC connection has been completed to the new base station 6 g-02, at operation 6 g-65. The new base station 6 g-02 resumes the DRBs if it receives the RRC connection resumption completion message. If the DRBs are released, the new base station 6 g-02 performs a procedure of newly generating the DRBs, whereas if the DRBs are suspended, the new base station 6 g-02 performs procedures of correcting and resuming paths of the DRBs, at operation 6 g-70. Then, the new base station 6 g-02 requests the old base station 6 g-03 to release the terminal context, at operation 6 g-75. Thereafter, the terminal 6 g-01 transmits/receives data to/from the network in an RRC connection state, at operations 6 g-80 and 6 g-85.

The PDCP control PDU may have the following structures.

TABLE 1 PDCP Control PDU Format 1 D/C DPU Type R NCC

TABLE 2 PDCP Control PDU Format 1 D/C DPU Type NCC R

The PDCP control PDU is an unencrypted PDU, and may include the NCC as described above. The PDCP control PDU may have the size of one byte, in which NCC of 3 bits, PDU Type of 3 bits, D/C of one bit, and reservation of one bit are included. If the D/C of one bit is “0”, it may indicate a control PDU, whereas if the D/C is “1”, it may indicate a data PDU. The PDU Type of 3 bits may be newly defined in 011-111 for NCC transmission.

FIG. 6H is a diagram explaining the operation of a terminal according to the (6-2)-th embodiment of the present disclosure.

Referring to FIG. 6H, if the base station determines to suspend an RRC connection of the terminal in a state where the terminal and the network transmit/receive data to/from each other, at operation 6 h-05, and transmits an RRC control message (RRC connection release message) including specific control information to the terminal, the terminal receives the RRC control message, at operation 6 h-10. The specific information of the RRC connection release message may be a resume identity to be used when the terminal resumes the RRC connection and paging region information. The terminal that has received the RRC control message (RRC connection release message) including the control information suspends all SRBs and DRBs, and stores the terminal context. The terminal context (that is also called a UE context) may include, for example, radio bearer configuration information, security key information, and radio measurement configuration information.

Then, the terminal performs an operation of determining whether to continuously stay in the current cell or to move to a new cell, i.e., cell reselection operation, in consideration of the downlink channel quality of the current serving cell and the downlink channel quality of a neighbor cell. If a specific reason for resuming the connection occurs at a certain time, for example, if new uplink data occurs in the terminal, at operation 6 h-15, the terminal starts a random access process in the current serving cell to resume the RRC connection, at operation 6 h-20. In the random access process, the terminal is allocated with the uplink transmission resource for transmitting the specific RRC control message from the base station, and sends the RRC control message to the base station, at operation 6 h-20. The RRC control message is a control message for requesting the RRC connection resumption, and may include information on resume identity (hereinafter referred to as resume ID) allocated at operation 6 h-10, resumeCause, and shortResumeMAC-1. The control message is transmitted through uplink SRB0. The base station that has received the control message identifies the old base station that stores the terminal context through checking of the resume ID, receives the terminal context from the base station, and receives new security keys and NCC through operations 6 g-30, 6 g-35, and 6 g-40. The new base station may generate an unencrypted PDCP control PDU in order to transfer the NCC information to a terminal that does not know the new security configuration. The PDCP control PDU may include the NCC information. The base station transmits a control message for instructing the terminal to resume the RRC connection in order to resume the RRC connection through applying of SRB1 configuration, SRB2 configuration, and DRB configuration using the terminal context and the new security keys, and also transmits the unencrypted PDCP control PDU including the NCC. The control message is transmitted through SRB1, and the PDCP generates a MAC-I using the current new security key, and transmits the MAC-I in a state where the MAC-I is appended at the back of the RRC control message. The control message may include the NCC.

Since the terminal that has received the control message is unable to decode the control message, it first receives the NCC from the unencrypted PDCP control PDU, at operation 6 h-25 to transfer the NCC to an RRC layer, and the RRC layer generates new security keys using the NCC, target PCI and target frequency of the current cell, at operation 6 h-30. The security keys may include KeNB*. Further, in order to apply the new security keys, the PDCP and RLC of the SRB1 are reestablished. The terminal performs integrity verification through checking of the MAC-I based on the generated new security key and the PDCP of the established SRB1, and resumes the RRC connection using the information in the control message, at operation 6 h-30. More specifically, the terminal resumes the operations of the SRB2 and DRBs, and reestablishes RLC devices and PDCP devices of the SRB2 and DRBs to apply the newly generated security keys. The reestablishment of the RLC device means initialization of an RLC serial number and various kinds of variables, and the reestablishment of the PDCP device means initialization of a PDCP serial number and HFN to “0”. After completion of the above-described procedure, the terminal sends a control message indicating that the resumption of the RRC connection has been completed to the base station, at operation 6 h-35.

FIG. 6I is a diagram illustrating the configuration of a terminal according to an embodiment of the present disclosure.

Referring to FIG. 6I, the terminal includes an RF processor 6 i-10, a baseband processor 6 i-20, a storage unit 6 i-30, and a controller 6 i-40.

The RF processor 6 i-10 performs a function for transmitting and receiving a signal through a radio channel, such as signal band conversion and amplification. That is, the RF processor 6 i-10 performs up-conversion of a baseband signal provided from the baseband processor 6 i-20 into an RF-band signal to transmit the converted signal to an antenna, and performs down-conversion of the RF-band signal received through the antenna into a baseband signal. For example, the RF processor 6 i-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC. Although only one antenna is illustrated in the drawing, the terminal may be provided with a plurality of antennas. Further, the RF processor 6 i-10 may include a plurality of RF chains.

The baseband processor 6 i-20 performs conversion between a baseband signal and a bit string in accordance with the PHY standard of the system. For example, during data transmission, the baseband processor 6 i-20 generates complex symbols by encoding and modulating a transmitted bit string. Further, during data reception, the baseband processor 6 i-20 restores a received bit string by demodulating and decoding the baseband signal provided from the RF processor 6 i-10. For example, in the case of following an OFDM method, during data transmission, the baseband processor 6 i-20 generates complex symbols by encoding and modulating a transmitted bit string, performs mapping of the complex symbols on subcarriers, and then configures OFDM symbols through the IFFT operation and CP insertion. Further, during data reception, the baseband processor 6 i-20 divides the baseband signal provided from the RF processor 6 i-10 in the unit of OFDM symbols, restores the signals mapped on the subcarriers through the FFT operation, and then restores the received bit string through demodulation and decoding.

The baseband processor 6 i-20 and the RF processor 6 i-10 transmit and receive the signals as described above. Accordingly, the baseband processor 6 i-20 and the RF processor 6 i-10 may be called a transmitter, a receiver, a transceiver, or a communication unit. Further, in order to support different radio connection technologies, at least one of the baseband processor 6 i-20 and the RF processor 6 i-10 may include a plurality of communication modules. Further, in order to process signals of different frequency bands, at least one of the baseband processor 6 i-20 and the RF processor 6 i-10 may include different communication modules.

The storage unit 6 i-30 stores therein a basic program for an operation of the terminal, application programs, and data of configuration information. The storage unit 6 i-30 provides stored data in accordance with a request from the controller 6 i-40.

The controller 6 i-40 controls the whole operation of the terminal. For example, the controller 6 i-40 transmits and receives signals through the baseband processor 6 i-20 and the RF processor 6 i-10. Further, the controller 6 i-40 records or reads data in or from the storage unit 6 i-30. Further, the controller 6 i-40 controls suspension and operation resumption of the SRB and DRB. For this, the controller 6 i-40 may include at least one processor. For example, the controller 6 i-40 may include a CP performing a control for communication and an AP controlling an upper layer, such as an application program. The controller 6 i-40 may include a multi-connection processor 6 i-42.

FIG. 6J is a diagram illustrating the configuration of a base station according to an embodiment of the present disclosure.

Referring to FIG. 6J, the base station includes an RF processor 6 j-10, a baseband processor 6 j-20, a backhaul communication unit 6 j-30, a storage unit 6 j-40, and a controller 6 j-50.

The RF processor 6 j-10 performs a function for transmitting and receiving a signal through a radio channel, such as signal band conversion and amplification. That is, the RF processor 6 j-10 performs up-conversion of a baseband signal provided from the baseband processor 6 j-20 into an RF-band signal to transmit the converted signal to an antenna, and performs down-conversion of the RF-band signal received through the antenna into a baseband signal. For example, the RF processor 6 j-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC. Although only one antenna is illustrated in the drawing, the first connection node may be provided with a plurality of antennas. Further, the RF processor 6 j-10 may include a plurality of RF chains.

The baseband processor 6 j-20 performs conversion between a baseband signal and a bit string in accordance with the PHY standard of the first radio connection technology. For example, during data transmission, the baseband processor 6 j-20 generates complex symbols by encoding and modulating a transmitted bit string. Further, during data reception, the baseband processor 6 j-20 restores a received bit string by demodulating and decoding the baseband signal provided from the RF processor 6 j-10. For example, in the case of following an OFDM method, during data transmission, the baseband processor 6 j-20 generates complex symbols by encoding and modulating a transmitted bit string, performs mapping of the complex symbols on subcarriers, and then configures OFDM symbols through the IFFT operation and CP insertion. Further, during data reception, the baseband processor 6 j-20 divides the baseband signal provided from the RF processor 6 j-10 in the unit of OFDM symbols, restores the signals mapped on the subcarriers through the FFT operation, and then restores the received bit string through demodulation and decoding. The baseband processor 6 j-20 and the RF processor 6 j-10 transmit and receive the signals as described above. Accordingly, the baseband processor 6 j-20 and the RF processor 6 j-10 may be called a transmitter, a receiver, a transceiver, or a communication unit.

The backhaul communication unit 6 j-30 provides an interface for performing communication with other nodes in the network.

The storage unit 6 j-40 stores therein a basic program for an operation of the master base station, application programs, and data of configuration information. In particular, the storage unit 6 j-40 may store information on a bearer allocated to the connected terminal and the measurement result reported from the connected terminal. Further, the storage unit 6 j-40 may store information that becomes a basis of determination whether to provide or suspend a multi-connection to the terminal. Further, the storage unit 6 j-40 provides stored data in accordance with a request from the controller 6 j-50.

The controller 6 j-50 controls the whole operation of the master base station. For example, the controller 6 j-50 transmits and receives signals through the baseband processor 6 j-20 and the RF processor 6 j-10 or through the backhaul communication unit 6 j-30. Further, the controller 6 j-50 records or reads data in or from the storage unit 6 j-40. For this, the controller 6 j-50 may include at least one processor. The controller 6 j-50 may include a multi-connection processor 6 j-52.

While the present disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. 

What is claimed is:
 1. A method performed by a terminal in a wireless communication system, the method comprising: receiving a first radio resource control (RRC) message for a suspension of an RRC connection, the first RRC message including a resume identity; suspending at least one data radio bearer (DRB) and at least one signaling radio bearer (SRB) based on the first RRC message; storing a security parameter; performing a cell reselection during the suspension of the RRC connection; performing a random access procedure in case that an uplink data to be transmitted occurs during the suspension of the RRC connection; obtaining an uplink transmission resource based on the random access procedure; transmitting, to a base station, a second RRC message for requesting a resumption of a suspended RRC connection through an SRB0 based on the uplink transmission resource, the second RRC message including the resume identity; receiving, from the base station, a third RRC message for resuming the suspended RRC connection through an SRB1 as a response to the second RRC message, the third RRC message including a next hop chaining count (NCC); resuming an SRB2 and the at least one DRB based on the third RRC message; verifying an integrity of the third RRC message based on the security parameter; deriving a security key based on the NCC included in the third RRC message; and transmitting, to the base station, a message which is ciphered using the security key, wherein a ciphering is deactivated based on the first RRC message and the ciphering is activated in case that the integrity of the third RRC message is verified successfully, and wherein an integrity protection is applied to the third RRC message based on the security parameter and the ciphering is not applied to the third RRC message.
 2. The method of claim 1, wherein the SRB1 is not in a suspended state before receiving the third RRC message, and wherein the SRB0 is kept based on the receiving of the first RRC message.
 3. The method of claim 1, further comprising: restoring a packet data convergence protocol (PDCP) state for the SRB2 and at least one DRB and re-establishing PDCP entities for the SRB2 and the at least one DRB based on the third RRC message.
 4. A terminal in a wireless communication system, the terminal comprising: a transceiver; and a controller configured to: receive, via the transceiver, a first radio resource control (RRC) message for a suspension of an RRC connection, the first RRC message including a resume identity, suspend at least one data radio bearer (DRB) and at least one signaling radio bearer (SRB) based on the first RRC message, store a security parameter, perform a cell reselection during the suspension of the RRC connection, perform a random access procedure in case that an uplink data to be transmitted occurs during the suspension of the RRC connection, obtain an uplink transmission resource based on the random access procedure, transmit, to a base station via the transceiver, a second RRC message for requesting a resumption of a suspended RRC connection through an SRB0, the second RRC message including the resume identity, receive, from the base station via the transceiver, a third RRC message for resuming the suspended RRC connection through an SRB1 as a response to the second RRC message, the third RRC message including a next hop chaining count (NCC), resume an SRB2 and the at least one DRB based on the third RRC message, verify an integrity of the third RRC message based on the security parameter, derive a security key based on the NCC included in the third RRC message, and transmit, to the base station, a message which is ciphered using the security key, wherein a ciphering is deactivated based on the first RRC message and the ciphering is activated in case that the integrity of the third RRC message is verified successfully, and wherein an integrity protection is applied to the third RRC message based on the security parameter and the ciphering is not applied to the third RRC message.
 5. The terminal of claim 4, wherein the SRB1 is not in a suspended state before receiving the third RRC message, and wherein the SRB0 is kept based on the receiving of the first RRC message.
 6. The terminal of claim 4, wherein the controller is further configured to: restore a packet data convergence protocol (PDCP) state for the SRB2 and the at least one DRB and re-establish PDCP entities for the SRB2 and the at least one DRB based on the third RRC message.
 7. A method performed by a base station in a wireless communication system, the method comprising: transmitting, to a terminal, a first radio resource control (RRC) message for a suspension of an RRC connection, the first RRC message including a resume identity; storing a security parameter; performing a random access procedure in case that an uplink data to be transmitted occurs during the suspension of the RRC connection; receiving, from the terminal, a second RRC message for requesting a resumption of a suspended RRC connection through a signaling radio bearer (SRB) 0 based on an uplink transmission resource obtained according to the random access procedure, the second RRC message including the resume identity; transmitting, to the terminal, a third RRC message for resuming the suspended RRC connection through an SRB1 as a response to the second RRC message, wherein the third RRC message includes a next hop chaining count (NCC); and receiving, from the terminal, a message which is ciphered using a security key, wherein the security key is derived based on the NCC, wherein an SRB2 and at least one data radio bearer (DRB) are resumed based on the third RRC message, wherein a ciphering is deactivated based on the first RRC message and the ciphering is activated in case that an integrity of the third RRC message is verified successfully, wherein an integrity protection is applied to the third RRC message based on the security parameter and the ciphering is not applied to the third RRC message, and wherein a cell reselection is performed during the suspension of the RRC connection.
 8. The method of claim 7, further comprising: acquiring the security key and bearer configuration information for the terminal based on the second RRC message.
 9. The method of claim 7, wherein the at least one DRB and at least one SRB are suspended while the SRB0 is kept based on the first RRC message.
 10. The method of claim 7, wherein a packet data convergence protocol (PDCP) state for the SRB2 and the at least one DRB is restored and PDCP entities for the SRB2 and the at least one DRB are re-established based on the third RRC message.
 11. A base station in a wireless communication system, the base station comprising: a transceiver; and a controller configured to: transmit, to a terminal via the transceiver, a first radio resource control (RRC) message for a suspension of an RRC connection, the first RRC message including a resume identity, store a security parameter, perform a random access procedure in case that an uplink data to be transmitted occurs during the suspension of the RRC connection, receive, from the terminal via the transceiver, a second RRC message for requesting a resumption of a suspended RRC connection through a signaling radio bearer (SRB) 0 based on an uplink transmission resource obtained according to the random access procedure, the second RRC message including the resume identity, transmit, to the terminal, a third RRC message for resuming the suspended RRC connection through an SRB1 as a response to the second RRC message, wherein the third RRC message includes a next hop chaining count (NCC), and receive, from the terminal, a message which is ciphered using a security key, wherein the security key is derived based on the NCC, wherein a ciphering is deactivated based on the first RRC message and the ciphering is activated in case that an integrity of the third RRC message is verified successfully, wherein an integrity protection is applied to the third RRC message based on the security parameter and the ciphering is not applied to the third RRC message, and wherein a cell reselection is performed during the suspension of the RRC connection.
 12. The base station of claim 11, wherein the controller is further configured to acquire the security key and bearer configuration information for the terminal based on the second RRC message.
 13. The base station of claim 11, wherein at least one DRB and at least one SRB are suspended while the SRB0 is kept based on the first RRC message.
 14. The base station of claim 11, wherein a packet data convergence protocol (PDCP) state for an SRB2 and at least one DRB is restored and PDCP entities for the SRB2 and the at least one DRB are re-established based on the third RRC message. 